Mukhtasar Muslim (Abridged) 391 — About Witr prayer

Umm al-Mu'mineen Aisha Siddiqa (may Allah be pleased with her) says that the Messenger of Allah (peace and blessings be upon him) performed Witr in the early part of the night, in the middle, and in the last part of the night, up until the time of Fajr.