The Most Important Basis that the State is built upon:
The Principle of Adherence to the Shariah Rule is one of the Most Important Basis that the State and the Life of the People is Built Upon

Forsaking the value of adherence to Shariah rules which is one of the basis that the state is built on, and one of  the foundations upon which the lives of individuals are based on, had a great impact on the lives of the Muslims - whether by adopting of rules not from Islam considering them from Islam even if by name by the state in the days of the Ottomans, or due to the neglect of individuals regarding the principle of adhering to the rules in their daily lives - was one of main reasons that led to the destruction of the Islamic State and the most important cause why the Muslims are in this current humiliation and degradation. So it was imperative that Muslims aim for complete conservation of the thoughts that relate to the Shariah rulings resulting in discipline in the individual's behavior, and discipline in the behavior of the Ummah in the conduct of State.

As for forsaking the value of the basis upon which the lives of individuals are built on, it manifests in the neglect of some individuals to the principle of adherence to the Shari'ah rules in their daily lives, whether in their individual behavior, or in their relationships with people,  majority of them and public opinion, overriding the relations of individuals, do not give weight to the Shariah rules. It does not even manifest, while adherence to Shariah rules is the basis of life and is the fruit of faith and upon it, the discipline of behavior must be based. The verses that indicate this are definite in meaning showing the obligation of adherence to the Shariah rules. Allah (swt) says:

[الم ترالى الذين يزعمون أنهم امنوا بما انزل إليك وما انزل من قبلك يريدون أن يتحاكموا إلى الطاغوت وقد أمروا أن يكفروا به ويريد الشيطان أن يضلهم ضلالا بعيدا، وإذا قيل لهم تعالوا إلى ما انزل الله والى الرسول رأيت المنافقين يصدون عنك صدودا]

"Have you not seen those who claim to have believed in what was revealed to you, [O Muhammad], and what was revealed before you? They wish to refer legislation to Taghut, while they were commanded to reject it; and Satan wishes to lead them far astray. And when it is said to them, "Come to what Allah has revealed and to the Messenger," you see the hypocrites turning away from you in aversion." [An-Nisaa': 60-61]

[فلا وربك لا يؤمنون حتى يحكموك فيما شجر بينهم ثم لا يجدوا في أنفسهم حرجا مما قضيت ويسلموا تسليما]

"But no, by your Lord, they will not [truly] believe until they make you, [ O Muhammad], judge concerning that over which they dispute among themselves and then find within themselves no discomfort from what you have judged and submit in [ full, willing] submission" [An-Nisaa': 65]

[وما آتاكم الرسول فخذوه وما نهاكم عنه فانتهوا واتقوا الله إن الله شديد العقاب]

"And whatever the Messenger has given you - take; and what he has forbidden you - refrain from. And fear Allah; indeed, Allah is severe in penalty" [Al-Hashr: 7]

These verses are definitive (qat'iy udalalah) in meaning, indicating the obligation of adherence to the Shariah rules, Allah (swt) commanded Muslims to take whatever the Messenger of Allah (saw) has brought from that which He (swt) has made obligatory upon them or made permissible for them. He commanded them to abstain from what He (swt) has made  prohibited for them and what is detestable for them, any request that came from the Prophet was from Allah is an obligation to adhere to, whether it is definitive command like the obligations or non-definitive request like the recommended actions (mandubat), or the request is definitive to abstain from the action like the prohibitions or non-definitive request to abstain from the actions like the detestable actions (makruhaat), or if there is a choice between taking the action or leaving it, like the permissible actions (mubah), all of this come under the saying of Allah:

[وما آتاكم الرسول فخذوه وما نهاكم عنه فانتهوا واتقوا الله إن الله شديد العقاب]

"And whatever the Messenger has given you - take; and what he has forbidden you - refrain from. And fear Allah; indeed, Allah is severe in penalty" [Al-Hashr: 7]

This is because the word "Ma" (whatever) is general and includes all the Shariah rules, the verse was revealed regarding the distribution of booties between the Muhajiroon  and excluded the Ansar, i.e. it was revealed to expose a rule from the Shariah rules, its context is regarding a Shariah rule which was proved by the action of the Prophet (saw). The verse came in the general format: "Ma" "ما" ("Whatever He brought" and "whatever he told to abstain from") it encompasses all the Shariah rules. If this verse is linked to the saying of Allah (swt):

[فليحذر الذين يخالفون عن أمره أن تصيبهم فتنة أو يصيبهم عذاب اليم]

"So let those beware who dissent from the Prophet's order, lest fitnah strike them or a painful punishment" [An-Nur: 63]

It indicates the command in His saying "فخذوه" "Take it" and" "فانتهوا " Abstain from it" as obligatory, this is why it is an obligation upon every Muslim to adopt the Shariah rules and adhere to them.  The Qur'an has confirmed this meaning  definitively in its negation of faith from the one who rules by other than what the Prophet has brought i.e. by other Shariah than Islam, because it is the Message of Islam. He (swt) says:

[فلا وربك لا يؤمنون حتى يحكموك]

"But no, by your Lord, they will not [truly] believe until they make you, [O Muhammad], judge". Then He (swt) did not restrict the belief to the reference in judgment to the Prophet but added the condition of being satisfied with the judgment , He (swt) says:

[ثم لا يجدوا في أنفسهم حرجا مما قضيت ويسلموا تسليما]

"...and then find within themselves no discomfort from what you have judged and submit in [full, willing] submission", which indicates that it is not enough to adhere to the Shariah rule out of fear of the authority, but the Muslim must be comfortable and submit completely to it.

It was narrated that a Jew and a hypocrite had a dispute, the hypocrite wanted Ka'b Ibn Al-Ashraf to judge between them, and the Jew wanted the Prophet (saw) to be the judge, they went to the Prophet (saw) and He (saw) gave a judgment in favour of the Jew. The hypocrite did not accept the judgment and the verse was revealed:

[فلا وربك لا يؤمنون]

"But no, by your Lord, they will not [truly] believe".

The Qur'an did not stop at this but it condemned those who resort to a judgment other than what was brought by the Prophet from the Shariah of Islam and describes it as resorting to Taghoot (judgment of the tyrant) and condemned them for doing so. Ibn Abi Hatim and Tabaraani extracted through an accurate Sanad (chain of narrations) from Ibn Abbas, that he said, "Abu Barza Al-Aslami was a monk who judges in disputes between the Jews, some  Muslims decided to refer to him in their disputes, so Allah (swt) revealed:

[الم تر إلى الذين يزعمون أنهم امنوا]

"Have you not seen those who claim to have believed?" which indicates clearly that reference to other than Shariah rules is reference to the Taghoot. Allah (swt) said that the Shaiytan wants to lead astray those who do so.

Along with verses came explicit Ahadeeth indicating the obligation of adherence to Shariah rules, He (saw) said, «تركت فيكم ما إن تمسكتم به لن تضلوا كتاب الله وسنتي» "I left with you that which if you adhere to, you shall never be astray, the Book of Allah and my Sunnah". The Prophet (saw) said: «من أحدث في أمرنا هذا ما ليس منه فهو رد» وفي رواية «من عمل عملا ليس عليه أمرنا فهو رد» "Who invents in our matter which is not from it, it is rejected" and in another narration: "Whoever does an action not in accordance to our matter, it is rejected".

Muslim narrated from Jabir Ibn Abdullah that the Messenger of Allah (saw) used to say in his speech: «أما بعد فإن خير الحديث كتاب الله وخير الهدي هدي محمد، وشر الأمور محدثاتها وكل بدعة ضلالة» "Verily, the best of speech is the Book of Allah and the best of guidance is that of Muhammad (saw), the worst of matters are innovations and each bid'ah (innovation) is misguidance".

Tirmithi narrated on the authority of Al Arbadh from Sariyah said:

وروى الترمذي عن العرباض عن سارية قال "صلى بنا رسول الله صلى الله عليه وسلم ذات يوم ثم اقبل علينا فوعظنا موعظة بليغة ذرفت منها العيون ووجلت القلوب، فقال قائل يا رسول الله كأن هذه موعظة مودع فماذا تعهد إلينا فقال: «أوصيكم بتقوى الله والسمع والطاعة لولاة الأمر وإن كان عبدا حبشيا فإن من يعش منكم فسيرى اختلافا كثيرا فعليكم بسنتي وسنة الخلفاء الراشدين المهديين، تمسكوا بها وعضوا عليها بالنواجذ وإياكم ومحدثات الأمور فان كل محدثة بدعة وكل بدعة ضلالة

"The Prophet (saw) led us in prayer one day, then he approached us and offered us a heart-felt advice that made our eyes tear and sent fear into our hearts, a man said: O Messenger of Allah (saw), this is like an advice from someone departing, so what do you want to leave us with, He (saw) said: I advise you to have taqwa in Allah and to hear and obey your ruler even if he was an Abassynian slave, those who live will see many differences, so resort to my Sunnah and the Sunnah of the guided Khaleefs, hold on to it tightly and (bite on it with your molars) and refrain from innovation in matters, for each innovation is Bid'ah and each Bid'ah is misguidance."

What is meant by the Sunnah of the Prophet (saw) is His saying, action, and consent, and it is what is known as the Sunnah from the Shariah evidences, and the meaning is not the recommended actions or Nawafil (supererogatory prayers) or to emulate the Prophet (saw). What is meant by the Sunnah of the guided Khulafaa' is that which they follow in the implementation of Shariah rules i.e. the method that they follow. What is meant by the guided Khulafaa' is all the guided Khulafaa', and not just the four, whether he was from the early days of the Khulafaa' like Omar Ibn Abdul Aziz, or whether he will be from the Khulafaa' of the future. What is meant by Bid'a (innovation) is all that is contrary to the Shariah. I.e. anything not from Shariah rules, and not just in personal worships only. Ibn Hajar has extracted in his Sawa'iq from Abi sa'eed Al Khudri from the Prophet (saw) that he said: «إني تركت فيكم كتاب الله عز وجل وسنتي فاستنطقوا القرآن بسنتي» "I left with you the Book of Allah Azza wa Jal and my Sunnah so refer to the Qur'an and my Sunnah in your actions".

These Ahadeeth indicate the adherence to the Book of Allah and the Sunnah of His Messenger i.e. adherence to the Shariah rules, it proves the adherence to Shariah rules. The Prophet (saw) did not stop at commanding the adherence in the Book and Sunnah but He (saw) warned from following anything other than them when He (saw) warned of following the way of others. Bukhari narrated from Abu Sa'eed al-Khudri from the Prophet (saw) that he said: «لتتبعن سنن من كان قبلكم شبرا بشبرا وذراعا بذراع حتى لو دخلوا جحر ضب تبعتموهم» "You will follow the wrong ways, of your predecessors so completely and literally that if they should go into the hole of a lizard, you too will go there." We said, "O Allah's Messenger! Do you mean the Jews and the Christians?" He replied, "Whom else?"

This hadeeth is condemning this action; it is a definitive prohibition, because it consists of prohibition and condemnation for the one who does the action. The Prophet (saw) used to prohibit asking the people of the Books about issues, because it is like referring to other than the Book and Sunnah, i.e. other than the Shariah rules, the Prophet (saw) said «لا تسألوا أهل الكتاب عن شيء» "Do not ask the people of the Book about anything". Bukhari narrated from Abdullah Ibn Abdullah that Ibn Abbas (ra) said, "How do you ask the people of the Book about a thing when your Book which was revealed to the Messenger of Allah is the most recent one, you read it in its early days."

All of these Ahadeeth indicate the warning from taking anything from other than the Book and Sunnah, i.e. forbidding taking anything from other than the Shariah rules which confirms the absolute adherence to Shariah rules.

These evidences provide non-debatable proof that it is obligatory to adhere to Shariah rules and indicate that it is a basis in the individual life of the Muslim, its negligence by some in their daily lives and its non-manifestation in relationships between people has led to the loss of the basic value that the daily life of individuals is built on and the basis that relationships between people are built upon. Therefore it's pointless to establish an Islamic State by people who lost the basis upon which the Islamic life is built upon for the individual and the basis that the relationships between people is built upon. This is why one of the most burdens on the shoulders of the Dawah carriers in their work to resume the Islamic way of life and carrying the Islamic Dawah to the world is to work to clarify this basic value which the life of Individuals is built upon and to try to find public opinion within the masses for this basic value which the basis of relationships between people is built upon, This is the most important action to establish the rule upon the Islamic thought, all of this is possible by making the Shariah rules an attribute of the Muslims and by making  it alone dominate the people.