It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her) that she said: The Messenger of Allah (peace and blessings be upon him) came to me after Asr and prayed two rak'ahs. I said: O Messenger of Allah, what are these two rak'ahs? He (peace and blessings be upon him) said: "I used to pray them before Asr; then some people came to me and kept me busy, so I have prayed them now."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19943