are invalid—then we say:

We have already cited evidence from the Book, the Sunnah, and transmitted reports establishing the general obligation to fulfil covenants and conditions, and that the point is that fulfilling them is obligatory. On this understanding, the obligation to fulfil them entails their permissibility: if fulfilling them is obligatory, they cannot be invalid; and if they are not invalid, they are permissible.

This is because his words, “not in the Book of Allah,” apply only to what is absent from the Book of Allah both in its general provisions and in its specific provisions. Whatever the Book of Allah establishes as permissible through its general provisions is indeed in the Book of Allah. For when we say, “This is in the Book of Allah,” we include what it contains both specifically and generally. This is how we understand the words of Allah Most High:

“And We have sent down to you the Book as a clarification of all things,”

and His words:

“But a confirmation of what came before it and a detailed explanation of all things,”

and His words:

“We have neglected nothing in the Book.”

This last verse applies here according to those who understand “the Book” to mean the Quran. According to those who understand it to mean the Preserved Tablet, however, it is not applicable here.

This is demonstrated by the fact that a condition whose permissibility is established by the Sunnah or scholarly consensus is valid by agreement. It must therefore be in the Book of Allah. It may not be specifically mentioned in the Book of Allah, but the Book of Allah commands us to follow the Sunnah and the path of the believers. In this sense, it is in the Book of Allah. For whatever encompasses an encompassing whole also encompasses its contents, and evidence establishing a proof is itself proof in this respect.