It is narrated from Sayyiduna Uqbah bin Amir (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) asked Sayyiduna Abu Bakr (may Allah be pleased with him): "When do you pray witr?" He said: I pray two rak'ahs at a time, then I pray witr before I sleep. The Messenger of Allah (peace and blessings be upon him) said to him: "A cautious believer." Then he (peace and blessings be upon him) asked Sayyiduna Umar bin al-Khattab (may Allah be pleased with him): "How do you pray witr?" He said: I pray two rak'ahs at a time, then I sleep and pray witr in the last part of the night. The Prophet (peace and blessings be upon him) said: "A strong believer."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14909