They (i.e. Upright scholars and their Students) clarify the rulings of the Islamic religion for the people in all spheres of life that requires clarification
Shaikh Muhammad Amaan Al-Jaami (rahimahullaah)
Indeed, the call to Islaam comprises of various fields and has different procedures; and among its procedures is the establishment of assemblies and summits in which men of sound Islamic views and the Jurists of the Muslims meet in order to solve the problems of the era. They refute the doubts that arise about Islaam and the (sound) creed of the Muslims. They clarify the rulings of the Islamic religion for the people in all spheres of life that requires clarification-and how numerous are those in need of clarification-so that the people can be upon clarity in their religious and worldly affairs. This is (carried out) under the auspices of the Book (i.e. the Qur’aan) and (authentic) Sunnah, so that people are removed from darkness and (entered) into light. And there is no (other) path of exit from the darkness of ignorance and Pre-Islamic (practices and beliefs) except by way of the understanding in the Book and the Sunnah. This is the job of the Messengers ( عليهم الصلاة والسلام), beginning with the first of them Nuh ( عليه الصلاة والسلام) to the last of them-their leader, Muhammad (صلى الله عليه وسلم). Allaah (The Most High) addressed His noble Messenger Muhammad ( صلى الله عليه وسلم), whilst clarifying what the Job of His Messenger and that of his followers is:
يَـٰٓأَيُّہَا ٱلنَّبِىُّ إِنَّآ أَرۡسَلۡنَـٰكَ شَـٰهِدً۬ا وَمُبَشِّرً۬ا وَنَذِيرً۬ا
وَدَاعِيًا إِلَى ٱللَّهِ بِإِذۡنِهِۦ وَسِرَاجً۬ا مُّنِيرً۬ا
وَبَشِّرِ ٱلۡمُؤۡمِنِينَ بِأَنَّ لَهُم مِّنَ ٱللَّهِ فَضۡلاً۬ كَبِيرً۬ا
”O Prophet (Muhammad)! Verily, We have sent you as witness, and a bearer of glad tidings, and a warner; And as one who invites to Allah [Islamic Monotheism, i.e. to worship none but Allah (Alone)] by His Leave, and as a lamp spreading light (through your instructions from the Qur’an and the Sunnah the legal ways of the Prophet). And announce to the believers (in the Oneness of Allah and in His Messenger Muhammad) the glad tidings, that they will have from Allah a Great Bounty.” [33:45-47]
In these three verses (i.e. Surah Al-Ahzaab), there is a clarification of the job of the Noble Messenger Muhammad (صلى الله عليه وسلم ) and that of his followers. And that is to call to Allaah [Islamic Monotheism] by the Permission and command of Allaah, upon clear sightedness and sure knowledge. Allaah said:
قُلۡ هَـٰذِهِۦ سَبِيلِىٓ أَدۡعُوٓاْ إِلَى ٱللَّهِۚ عَلَىٰ بَصِيرَةٍ أَنَا۟ وَمَنِ ٱتَّبَعَنِىۖ
Say (O Muhammad): “This is my way; I invite unto Allah (i.e. to the Oneness of Allah – Islamic Monotheism) with sure knowledge, I and whosoever follows me (also must invite others to Allah i.e. to the Oneness of Allah – Islamic Monotheism) with sure knowledge’’ [12:108]
Allaah obligated His Prophet with this generalised call and not specified to his people (i.e. the Arabs), which was the case with the Messengers before him (i.e. the call of the other Prophets was limited to their people); rather the Prophet’s Message is to call all the people. Allaah (The Most High) said: [وَمَآ أَرۡسَلۡنَـٰكَ إِلَّا ڪَآفَّةً۬ لِّلنَّاسِ] ”And We have not sent you (O Muhammad), except to all mankind.” [34:28]
This is an obligation (placed) upon the Messenger (صلى الله عليه وسلم ) and then upon his followers, so that they may be witnesses against all the people.
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[Abridged and slightly paraphrased: Source: نظام الأسرة في الإسلام (page8-9)]