Sayyiduna Ali narrates that the Messenger of Allah (peace and blessings be upon him) has performed Witr in every part of the night: in the early part of the night, in the middle of the night, and also in the last part of the night.
Hadith Referenceصحيح ابن خزيمه / جماع أبواب ذكر الوتر وما فيه من السنن / 1080