The Book of the Times (of Prayer)
6/36. Chapter:
Concession Allowing Prayer After 'Asr
Sunan an-Nasai
أَخْبَرَنِي مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى، قَالَ حَدَّثَنَا الْمُعْتَمِرُ، قَالَ سَمِعْتُ مَعْمَرًا، عَنْ يَحْيَى بْنِ أَبِي كَثِيرٍ، عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ أُمِّ سَلَمَةَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم صَلَّى فِي بَيْتِهَا بَعْدَ الْعَصْرِ رَكْعَتَيْنِ مَرَّةً وَاحِدَةً وَأَنَّهَا ذَكَرَتْ ذَلِكَ لَهُ فَقَالَ " هُمَا رَكْعَتَانِ كُنْتُ أُصَلِّيهِمَا بَعْدَ الظُّهْرِ فَشُغِلْتُ عَنْهُمَا حَتَّى صَلَّيْتُ الْعَصْرَ " .
It was narrated from Umm Salamah that the Prophet (ﷺ) once prayed two Rak'ahs after 'Asr in her house. She asked him about that and he said: "They are two Rak'ahs that I used to pray after Zuhr, but I got distracted and forgot them until I prayed 'Asr."
Reference : Sunan an-Nasa'i 579In-book reference : Book 6, Hadith 86English translation : Vol. 1, Book 6, Hadith 580