Silsilat al-Ahadith al-Sahihah

Abu Idris Khawlani says: I was sitting in a gathering of the noble Companions (may Allah be pleased with them), and among them was Sayyiduna Ubadah bin Samit (may Allah be pleased with him). They discussed the command regarding the Witr prayer; some said that the Witr prayer is obligatory, while others considered it Sunnah. Sayyiduna Ubadah bin Samit (may Allah be pleased with him) (presenting his opinion) said: I bear witness that I heard the Messenger of Allah (peace and blessings be upon him) say: "Jibreel came to me from Allah Almighty and said: O Muhammad! Allah Almighty has said to you: I have made five prayers obligatory upon your Ummah. Whoever performs them properly, with ablution, at their times, and with all their prostrations and requirements, has a covenant with Me that I will admit him to Paradise. And whoever meets Me having neglected them, there is no covenant for him with Me; if I wish, I will punish him, and if I wish, I will have mercy on him."

Sayyiduna Sa’d bin Abi Waqqas (may Allah be pleased with him) says: I used to perform the ‘Isha prayer in the Prophet’s Mosque, and after that, I would perform one rak’ah of Witr. I was told: Abu Ishaq! You perform only one rak’ah of Witr, you do not perform more, (what is the reason)? I said: Yes, I heard the Messenger of Allah (peace and blessings of Allah be upon him) say: “He acts with foresight who performs Witr before sleeping.”

It is narrated from Sayyidah Aisha (may Allah be pleased with her) that the Noble Prophet (peace and blessings be upon him) would (sometimes) pray five and (sometimes) seven rak'ahs of Witr.