Sayyidah Umm Salamah (may Allah be pleased with her) relates that it happened only once: the Messenger of Allah (peace and blessings be upon him) came to me one day after Asr and prayed two rak'ahs. I said: O Messenger of Allah, what prayer is this? You did not used to pray it. Has a prayer after Asr been revealed? He (peace and blessings be upon him) said: "No, but these are the two rak'ahs I used to pray after Zuhr. I was kept busy from them, so I made them up afterwards."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19888