to combine during the time of the first prayer, because it is not permissible to delay a prayer beyond its appointed time without an excuse, except with the intention of combining where this is permitted.

The evidence that it is not permissible to delay a prayer beyond its appointed time is that the Prophet ﷺ specified the prayers at particular times (1). Thus, the first prayer may not be delayed beyond its time except with the intention of combining, where its cause exists. It is therefore necessary to form the intention to combine before the time of the first prayer expires.

His statement, “provided that its time has not become too short to perform it,” means: provided that the time of the first prayer has not become too short to perform it. If its time has become too short to perform it, combining is invalid, because delaying the prayer until its time becomes too short to perform it is prohibited, while combining is a concession; and concessions may not be availed of through what is prohibited. Thus, if a travelling man lets the time pass until there remains only so much of the noon prayer’s time as is too short to perform it, and then intends to combine the noon prayer with the afternoon prayer, this intention is invalid, because it is prohibited to delay the prayer until the time becomes too short. Indeed, what is obligatory is to perform the entire prayer within its time.

So we say: Pray now according to the amount of its time that remains, and seek Allah’s forgiveness for the delay. The time of the second prayer will begin before you complete your prayer, so pray it—but not as a combined prayer; rather, as a prayer performed at the beginning of its time.

His statement, “and that the excuse continue until the time of the second prayer begins,” means that, for the combination to be valid, the excuse must continue until the time of the second prayer begins. If it does not continue, then combining is prohibited.