'A'isha observed that the Messenger of Allah (ﷺ) used to observe prayer in the night and the last of his (night) prayer was Witr.
Sahih Muslim Book 6, Hadith 158
← Previous Hadith He used to sleep in the early part of the night, and woke up in the latter part. If he then wished intercourse with his wife, he satisfied his desire, and then went to sleep; and when the first call to prayer was made he jumped up (by Allah, she, i. e. 'A'isha, did not say" he stood up" ), and poured water over him (by Allah she, i. e. 'A'isha, did not say that he took a bath but I know what she meant) and if he did not have an intercourse, he performed ablution, just as a man performs ablution for prayer and then observed two rak'ahs.

Sahih Muslim Book 6, Hadith 157 Next Hadith → He (the Holy Prophet) loved (that action) which one keeps on doing regularly. I said (to 'A'isha): When did he pray (at night)? She replied: When he heard the cock crow, he got up and observed prayer.

Sahih Muslim Book 6, Hadith 159