Sunan an-Nasai 15318
In-book no 582أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ أَنْبَأَنَا وَكِيعٌ، قَالَ حَدَّثَنَا طَلْحَةُ بْنُ يَحْيَى، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ بْنِ عُتْبَةَ، عَنْ أُمِّ سَلَمَةَ، قَالَتْ شُغِلَ رَسُولُ اللَّهِ صلى الله عليه وسلم عَنِ الرَّكْعَتَيْنِ قَبْلَ الْعَصْرِ فَصَلاَّهُمَا بَعْدَ الْعَصْرِ .
It was narrated that Umm Salamah said: "The Messenger of Allah (ﷺ) got distracted and did not pray the two Rak'ahs before 'Asr so he prayed them after 'Asr."