It is narrated from Hazrat Abu Mas'ud (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) used to offer Witr in the early, middle, and last parts of the night.
Hadith Referenceمسند احمد / مسند الأنصار رضي الله عنهم / 21877
Hadith Gradingحکم دارالسلام:إسناده ضعيف لانقطاعه، إبراهيم لم يسمع أبا عبدالله