Allah's Messenger (ﷺ) said, "Whoever could get one rak`a of a prayer, (in its proper time) he has got the prayer."
Sahih al-Bukhari Book 9, Hadith 56
← Previous Hadith Allah's Messenger (ﷺ) said, "Whoever could get one rak`a (of the Fajr prayer) before sunrise, he has got the (morning) prayer and whoever could get one rak`a of the `Asr prayer before sunset, he has got the (`Asr) prayer."

Sahih al-Bukhari Book 9, Hadith 55 Next Hadith → "The Prophet (ﷺ) forbade praying after the Fajr prayer till the sun rises and after the `Asr prayer till the sun sets."

Narrated Ibn `Abbas:

Some people told me the same narration (as above).

Sahih al-Bukhari Book 9, Hadith 57