Evidence of the Principles of Usul al-Fiqh and Fiqh

The questioner : Whether the fiqh principles or the principles established by the scholars of usul, do they have evidence from the Book or the Sunnah, or did they come as a result of ijtihad and knowledge of the rulings of the Shari'ah? Or does every principle have a proof?

The Shaykh : By Allah, the only thing we can say is that many of these principles are not applicable. And a section not far from them consists of specific madhhab principles that were stated to justify the branches that appeared in their madhhab, and there is no evidence from the Book and the Sunnah that obligates the Muslim to adopt them. But as for the first section of principles, they are undoubtedly, as I tell many of our children when they ask a question, and the questioner asks, "What is the evidence?" and it occurs to me from his question that he wants an explicit statement from Allah or the Messenger of Allah (peace and blessings be upon him). I say, "O people, do not imagine that every issue is the noble, clear, and explicit one that everyone shares in understanding, whether they are scholars or ignorant, readers or illiterate. No, and perhaps it is closer to examples. Yesterday or this morning, and I forgot. One of our known brothers asked me questions, among which was that he is a man who has the nisab for zakah. Then something came to him during the year. So when the hawl completed on the nisab, does he pay zakah on the nisab alone, or on the nisab and the new money that came to him? I told him, "This is paid from the total amount of money he has, even that which has not completed a hawl." He said, "How is this? The Messenger (peace and blessings be upon him) has the well-known hadith: 'Knowledge is two types, until he mentions the ruling upon it?' I told him, "Yes, this is a well-known hadith, but fiqh indicates what I told you." He said, "What is the evidence?" I told him, "The evidence is understanding." I explained the matter to him at length.
The Shaykh: I told him, "This understanding, my brother, is based on a deep understanding of general legal principles. Among them is the saying of Allah the Exalted: 'Indeed, Allah intends for you ease,' and so on, regarding the command of Allah. When I mentioned to him that either it must be said that every amount of money that enters a person's possession must be recorded at the time of its nisab, and this will undoubtedly lead to great hardship, especially for those with wealth, where perhaps every moment a nisab is recorded, this is a matter that is hardly... I had not finished my speech when he said, 'By Allah, it is correct, correct,' and I quickly clarified to him that the matter cannot be in the Shari'ah except in this way. The point is that the evidence from which legal rulings are derived, whether they are branches or principles, are not all in the same place of clarity and explanation for the general public. Therefore, we advise students of knowledge, so that they may be aware of the evidence for some of the scientific usul principles, to read the book Al-Ahkam fi Usul al-Ahkam by Ibn Hazm. Because in reality, I have not found a book in the science of usul in which its author commits to supporting every principle he adopts with evidence from the Book of Allah or a hadith from the hadith of the Messenger of Allah (peace and blessings be upon him) except this one. So the difficulty, the truth of it, is the narrowness of the scientific circle that these people resemble. The book is Al-Ahkam fi Usul al-Ahkam. Please.