[The Ruling on One Who Sold and “Included” His Partners]

Answer—and Allah, the Granter of success and aid: What is required in this situation is what the prevailing custom dictates. What appears to me, by customary standard, is that one who remains silent in such a case—while knowing of the sale—is deemed consenting. When custom recognizes silence as consent, that custom is acted upon, as is the madhhab, so long as it does not clash with a textual proof; and here, as it appears to me, it does not clash with any text. Indeed, it is related in the books of sīrah that the Prophet—May Allah bless him and his family and grant them peace—wrote a document among the people of Medina even though only a few from each group were present, and those present undertook the commitment on behalf of those behind them.
It is also related in the sīrah that the Prophet—May Allah bless him and his family and grant them peace—did likewise with the pilgrims of Medina at the Pledge of al-ʿAqabah: he asked them for twelve chiefs who would pledge on their own behalf and on behalf of those behind them… etc.
Accordingly, the claim of one who asserts that he neither sold nor approved the sale—while he knew of its occurrence and remained silent for a long period with no impediment preventing him from expressing disapproval—is not to be heard.
What is required is to persuade anyone making such a claim, and the door should not be opened to this; for it would lead to the spread of corruption concerning much of what is in people’s hands by way of sales, and then to abundant quarrelling and disputes.
Among the legal maxims is: “It is obligatory to carry Muslims’ contracts and transactions upon validity whenever possible,” and they said: “The default in transactions is validity.”
This maxim is sound. The proof of its soundness is that Allah Most High brought Islam while people were already transacting in sale, purchase, gift, partnership, vows, marriage, etc.; and He affirmed for them these transactions and forbade specific matters and particulars. Based on this, whatever transactions have occurred that the Law has affirmed are valid—so long as there is nothing in the transaction that the Lawgiver forbade. If there is something of that, then it is invalid, for it clashes with the text and contravenes the prohibition.
As for acts of worship, the default in them is invalidity until it is known—where knowledge is required—or thought likely—where likelihood suffices—that the act of worship has included all its conditions, remembrances, and pillars that are obligatory therein.
The proof for what we have stated is that acts of worship are legal acts made obligatory by the Law; thus they are not valid unless they conform to the Lawgiver’s command. If they do not conform to the Lawgiver’s command, they are un-legal and therefore invalid—such as prayer without purification, or not facing the qiblah, or without bowing, and the like.
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2