Sunan an-Nasa'i 578
سنن النسائي#578SahihIt was narrated from Abu Salamah that he asked 'Aishah about the two prostrations (Rak'ahs) that the Messenger of Allah (ﷺ) used to pray after 'Asr. She said:"He used to pray them before 'Asr, but if he got distracted or forgot them, he would pray them after 'Asr, and if he did a prayer he would be constant in it
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih Muslim
In-book reference: 6:85