It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her); she said: One day the Prophet (peace and blessings be upon him) came to me and prayed two rak'ahs after Asr, though I had never seen him (peace and blessings be upon him) pray them before. So I said: O Messenger of Allah! What are these two rak'ahs? He (peace and blessings be upon him) said: "The delegation of Banu Tamim came, so I could not pray the two rak'ahs after Zuhr; these are those."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19844