Abu Salamah says: I asked Sayyidah Aishah (may Allah be pleased with her): How was the prayer of the Prophet (peace and blessings be upon him) in Ramadan? She said: The Prophet (peace and blessings be upon him) did not pray more than eleven rak'ahs, either in Ramadan or outside Ramadan. He (peace and blessings be upon him) would pray four rak'ahs; do not even ask about their excellence and length! Then he (peace and blessings be upon him) would pray four rak'ahs, and there was no measure to their excellence and length. Then he (peace and blessings be upon him) would pray three rak'ahs. I said: O Messenger of Allah! Do you (peace and blessings be upon him) sleep before praying witr? He (peace and blessings be upon him) said: "O Aishah! My eyes sleep, but my heart stays awake."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4614