Allah's Messenger (ﷺ) offered witr prayer at different nights at various hours extending (from the `Isha' prayer) up to the last hour of the night.
Sahih al-Bukhari Book 14, Hadith 7
← Previous Hadith I asked Ibn `Umar, "What is your opinion about the two rak`at before the Fajr (compulsory) prayer, as to prolonging the recitation in them?" He said, "The Prophet (ﷺ) used to pray at night two rak`at followed by two and so on, and end the prayer by one rak`ah witr. He used to offer two rak`at before the Fajr prayer immediately after the Adhan." (Hammad, the sub-narrator said, "That meant (that he prayed) quickly.)"

Sahih al-Bukhari Book 14, Hadith 6 Next Hadith → The Prophet (ﷺ) used to offer his night prayer while I was sleeping across in his bed. Whenever he intended to offer the witr prayer, he used to wake me up and I would offer the witr prayer too.

Sahih al-Bukhari Book 14, Hadith 8