A man asked the Messenger of Allah ﷺ about the night prayer. The Messenger of Allah replied, "The night prayer is offered in pairs of two. When one of you fears the approach of dawn, let him pray a single rakah, which will make all that he has prayed witr."
أن رجلا سأل رسول الله ﷺ عن صلاة الليل، فقال رسول الله: صلاة الليل مثنى مثنى، فإذا خشي أحدكم الصبح صلى ركعة واحدة توتر له ما قد صلى.
Malik narrated it in Salat al-Layl (13) from Nafi and Abdullah bin Dinar, from Abdullah bin Umar, and he related the hadith. Bukhari narrated it in the Book of Witr (990) from Abdullah bin Yusuf, and Muslim in Salat al-Musafirin (749) from Yahya bin Yahya, both of them from Malik with the same wording.Muslim also narrated it by another route, from the hadith of Ayub and Budayl, both of them from Abdullah bin Shaqiq, from Abdullah bin Umar, that a man asked the Prophet ﷺ, while I was between him and the questioner, "Messenger of Allah, how is the night prayer performed?" He said, "Two by two. But when you fear the approach of dawn, pray one rakat, and make the last of your prayer an odd number." Then a man asked him again at the turn of the year, and I was in that same position relative to the Messenger of Allah ﷺ, and I do not know whether it was the same man or another man, and he gave him the same answer.As for what Abu Dawud (1295), Tirmidhi (597), Nasai (1666), and Ibn Majah (1322) all narrated by way of Shubah, from Yaala bin Ata, from Ali Bariqi, from Ibn Umar, from the Prophet ﷺ, where it states, "The night and day prayer is two by two," adding "the day," this addition is shadh (anomalous).Tirmidhi said, "The companions of Shubah differed regarding the hadith of Ibn Umar. Some of them made it a raised report and others made it stopped. It has also been narrated from Abdullah Umari, from Nafi, from Ibn Umar, from the Prophet ﷺ, something similar to this. The sahih view regarding Ibn Umar is that the Prophet ﷺ said, 'The night prayer is two by two,' and the trustworthy narrators reported this from Abdullah bin Umar, from the Prophet ﷺ, without mentioning the day prayer. It has also been narrated from Ubaydullah, from Nafi, from Ibn Umar, that he used to pray at night two by two and during the day four." End of quote.Ali Azdi was alone in narrating this addition, and Ibn Main, Ahmad, Nasai, Daraqutni, and others have criticized it on the grounds that the memorizing companions of Ibn Umar all narrated from him, from the Prophet ﷺ, "The night prayer is two by two," without any mention of the day. Ibn Rajab said that these narrators number more than fifteen individuals. See his Fath al-Bari (6/192).He also said, Imam Ahmad and others criticized this narration on the grounds that it has been reported from Ibn Umar that he used to pray four at a time during the day, and had he possessed an explicit text from the Prophet ﷺ on this matter, he would not have contradicted it. However, the preferred practice for voluntary daytime prayer is that it be performed two by two, and this is the view held by Malik, Shafii, Ahmad, and others. If someone performs voluntary daytime prayer in units of four, there is no harm in it, following the practice of Ibn Umar. Ishaq used to say, "For the day prayer I prefer four, though if one prays two rakats it is permissible." See Mughni (2/537–538).