Sahih Ibn Khuzaymah

And the explanation of the evidence that in the hadith of Sayyiduna Abdullah bin Amr, may Allah be pleased with him, the statement of the Messenger of Allah, peace and blessings be upon him, "Then when you have performed the Asr prayer, its time remains until the sun becomes yellow," by this, the Messenger of Allah, peace and blessings be upon him, meant the time of Asr prayer for one who has an excuse, necessity, or forgets, that if he remembers before the sun becomes yellow or when it becomes yellow, then he should perform the prayer. Similarly, by his statement, "Whoever catches one rak'ah of the Asr prayer before the sun sets, he has caught it completely," he meant that this is the time for one who has an excuse, necessity, or forgets the Asr prayer, that when he remembers, if it is possible for him to perform one rak'ah before the sun sets, then he should perform it. The Messenger of Allah, peace and blessings be upon him, did not mean that he has made it permissible for one without any excuse, necessity, or who remembers the Asr prayer, to delay the Asr prayer until the sun becomes yellow or to perform one rak'ah before the sun sets and the remaining three rak'ahs after sunset.