Sunan an-Nasa'i 516
سنن النسائي#516SahihIt was narrated from Abu Hurairah that the Prophet (ﷺ) said:"If any one of you catches the first prostration of 'Asr prayer before the sun sets, let him complete his prayer, and if he catches up with the first prostration of Fajr prayer before the sub rises, let him complete his prayer
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 - Bukhari And Muslim
In-book reference: 6:23