Sayyidah Asma' bint Umays (may Allah be pleased with her) said: When revelation came down upon the Messenger of Allah (peace and blessings be upon him), he (peace and blessings be upon him) would almost faint. One day revelation came down upon him (peace and blessings be upon him) while his (peace and blessings be upon him) head was in the lap of Ali (may Allah be pleased with him). The Messenger of Allah (peace and blessings be upon him) said to him: "Have you prayed Asr, O Ali?" He said: No, O Messenger of Allah. So he (peace and blessings be upon him) supplicated to Allah, and Allah brought the sun back for him until he prayed Asr. She said: "I saw the sun rise again after it had set, when it was brought back until he prayed Asr."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20762