Allah's Messenger said: "When Fajr begins, then every Salat of the night and Al-Witr have gone, so perform Al-Witr before Fajr begins."
Jami` at-Tirmidhi Book 3, Hadith 17
← Previous Hadith Allah's Messenger said: "Perform Witr before the morning comes upon you."

Jami` at-Tirmidhi Book 3, Hadith 16 Next Hadith → his father said: I heard Allah's Messenger saying: "There are no two Witr in one night."

Jami` at-Tirmidhi Book 3, Hadith 18