Masruq narrates from Sayyidah Aishah (may Allah be pleased with her) that the Prophet (peace and blessings be upon him) prayed witr in every part of the night, and he (peace and blessings be upon him) took the witr as far as the last part of the night.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4834