مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 601
Prayer
Observing Prayer Early in the Period - Section 1
وَعَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «مَنْ أَدْرَكَ رَكْعَةً مِنَ الصُّبْحِ قَبْلَ أَنْ تَطْلُعَ الشَّمْسُ فَقَدْ أَدْرَكَ الصُّبْحَ. وَمَنْ أَدْرَكَ رَكْعَةً مِنَ الْعَصْرِ قَبْلَ أَنْ تغرب الشَّمْس فقد أدْرك الْعَصْر»
Abu Huraira reported God’s Messenger as saying, “If anyone performs a rak'a of the Morning Prayer before sunrise, he has observed the Morning Prayer; and if anyone performs a rak'a of the afternoon prayer before sunset, he has observed the afternoon prayer.” (Bukhari and Muslim.)
Mishkat al-Masabih, 601مُتَّفَقٌ عَلَيْهِ (الألباني)