وَعَنْ أَبِي هُرَيْرَةَ رضى الله عنه
أَنَّ رَسُولَ اَللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «مَنْ أَدْرَكَ مِنْ اَلصُّبْحِ رَكْعَةً قَبْلِ أَنْ تَطْلُعَ اَلشَّمْسُ فَقَدْ أَدْرَكَ اَلصُّبْحَ، وَمَنْ أَدْرَكَ رَكْعَةً مِنْ اَلْعَصْرِ قَبْلَ أَنْ تَغْرُبَ اَلشَّمْسُ فَقَدْ أَدْرَكَ اَلْعَصْرَ»
The Prophet (sallallahu alayhi wa sallam) said: “He who prays a Raka of the Fajr prayer before the sun rises, has offered the dawn prayer in its time, and he who prays a Raka of the Asr prayer before the sun sets has offered the afternoon prayer.”.
Bulugh al-Maram 190, Book 2, The Book of Prayer, Hadith 11. 1 min read