His words: “But if they willingly remit any of it to you, then take it in satisfaction and ease” [al-Nisā’: 4]. The former verse concerns exchange transactions, whereas this verse concerns gratuitous transfers. He stipulated neither any particular wording nor any particular act as an indication of mutual consent and willing agreement. We know necessarily from people’s customary words and deeds that they ascertain mutual consent and willing agreement through various forms of speech and conduct.

We therefore say: mutual consent and willing agreement are present, and knowledge of them is certain in most customary contracts and evident in some cases. Whenever they are present, the legal ruling attaches to them, as indicated by the Quran. Some people may be driven by obstinacy in championing a particular opinion to deny what people know concerning mutual consent and willing agreement. No weight is given to such a denial, for self-evident truths are often denied because of concerted agreement and indoctrination in matters of reports and doctrines. What counts is a sound natural disposition that has not been opposed by anything that would alter it. This is why we have said that mass-transmitted reports yield certain knowledge when there is no collusion to lie, because sound natural dispositions do not concur in lying. When there is collusion and agreement, however, groups of people may agree upon a lie.

The second consideration is that these terms occur in the Book of Allah and the Sunnah of His Messenger, with legal rulings attached to them. Every term must have a definition. Some definitions are known through language, such as the sun, the moon, land, sea, heaven, and earth. Others are known through the Sharia, such as believer, disbeliever, and hypocrite, and such as prayer, zakat, fasting, and Hajj. Whatever has no definition in either language or the Sharia is referred to people’s custom, such as taking possession, mentioned in the Prophet’s words—may Allah bless him and grant him peace: “Whoever purchases food must not sell it until he takes possession of it.”