the option until tomorrow,” or “I have the option until nightfall,” it expires at the beginning of that time. This is because the starting point of a limit is included, whereas its endpoint is not. Thus, if he says, “Until tomorrow,” tomorrow itself is not included, and the option ends at dawn. “Until nightfall” means that the night is not included, so the option ends at sunset, as Allah the Exalted says:

“Then complete the fast until nightfall.” [al-Baqarah 2:187]

Some scholars have said that this should be referred to customary usage. Thus, when someone says, “Until tomorrow,” it may be understood as meaning until the opening of the market. In most cases, markets do not open at the dawn call to prayer, but rather after the sun has risen and people have gone out to the markets.

This is the correct view. Therefore, if it is customary among merchants that when they say, “Until tomorrow,” they mean until the market opens, then the term extends until the market opens. Yes, if there is no established custom, or if the custom is inconsistent, then we return to the linguistic meaning: linguistically, tomorrow begins at dawn, and “until nightfall” means until sunset. If, however, there is a custom whereby merchants gather after the night prayer and regard deferred terms as extending through the night—that is, the gathering after the night prayer—then this custom is to be followed.

This is a principle that we should know: “The reference point in the expressions and actions commonly used by people is custom.” If there is no custom, or if the custom is unsettled, we return to the linguistic meaning, unless a matter has a legally defined meaning. If it has a legally defined meaning, that takes precedence over all other meanings.

The author’s statement, “The one who holds the option may rescind, even if the other party is absent and displeased,” means that whoever holds the option—whether the seller, the purchaser, or both of them—has the right