(5) باب فِي وَقْتِ صَلاَةِ الْعَصْرِ
Abu Hurairah reported the Messenger of Allah (ﷺ) as saying:
If anyone says a rak'ah of the 'Asr prayer before sunset, he has observed (the 'Asr prayer), and if anyone performs a rak'ah of the Fajr prayer, he has observed (the Fajr prayer).
Reference: Sunan Abi Dawud 412
In-book reference: Book 2, Hadith 22
English translation: Book 2, Hadith 412