Catching one rak'ah before the time ends

Whoever catches one rak'ah of Fajr before sunrise has caught Fajr.

Narrated by Abu Hurairah

Whoever catches one rak'ah of the morning prayer before the sun rises has caught the morning prayer, and whoever catches one rak'ah of Asr before the sun sets has caught Asr.

Sahih al-Bukhari 579, Sahih Muslim 608

What this hadith teaches

This is for someone who was excused, for example who woke late: they must pray at once. It is not permission to delay deliberately.

Reference and grade

Grade
Sahih: agreed upon by al-Bukhari and Muslim
Narrator
Abu Hurairah

The hadith in Arabic نص الحديث

مَنْ أَدْرَكَ مِنَ الصُّبْحِ رَكْعَةً قَبْلَ أَنْ تَطْلُعَ الشَّمْسُ فَقَدْ أَدْرَكَ الصُّبْحَ، وَمَنْ أَدْرَكَ رَكْعَةً مِنَ الْعَصْرِ قَبْلَ أَنْ تَغْرُبَ الشَّمْسُ فَقَدْ أَدْرَكَ الْعَصْرَ

Arabic text of Sahih al-Bukhari 579, as given on sunnah.com.