The time for Witr prayer lasts from after ‘Isha’ prayer until the dawn begins. See question no. 46544.
Once dawn begins, the time for Witr is over, based on the words of the Prophet (peace and blessings of Allaah be upon him): “Pray Witr before morning comes.” Narrated by Muslim, 754.
Muslim also narrated from Ibn ‘Umar (may Allaah be pleased with him) that the Prophet (peace and blessings of Allaah be upon him) said: “Hasten to pray witr before dawn.”
And Muslim narrated (752) that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Witr is one rak’ah at the end of the night.”
Al-Tirmidhi narrated (469) from Ibn ‘Umar (may Allaah be pleased with him) that the Prophet (peace and blessings of Allaah be upon him) said: “When dawn comes, all the night prayers and Witr are over, so pray Witr before dawn comes.” Classed as saheeh by al-Albaani in Saheeh al-Tirmidhi.
Al-Bukhaari (472) and Muslim (749) narrated that the Prophet (peace and blessings of Allaah be upon him) said: “The night prayers are two (rak’ahs) by two, then when you think that morning (dawn) is about to begin, pray one (rak’ah) and it will make what you have prayed Witr (odd-numbered).”
Shaykh Ibn ‘Uthaymeen said:
This indicates that the time for Witr ends when the dawn comes, because it is a prayer with which the night prayers are concluded, so it cannot be done after the night has ended.
Majmoo’ Fataawa Ibn ‘Uthaymeen, 14/115
Some of the scholars are of the view that the time for Witr lasts after the dawn comes, until one has prayed Fajr, and they quoted as evidence the report narrated about some of the Sahaabah, that they prayed Witr after dawn had come and before the iqaamah was said for Fajr prayer.
Ibn Rushd al-Qurtubi said:
With regard to the time for Witr, the scholars are unanimously agreed that the time for it is from after ‘Isha’ prayer until dawn begins, because that was narrated through numerous isnaads from the Prophet (peace and blessings of Allaah be upon him). One of the strongest such reports is that narrated by Muslim from Abu Nadrah al-‘Awfi, which says that Abu Sa’eed told them that they asked the Prophet (peace and blessings of Allaah be upon him) about Witr and he said: “Witr comes before dawn.” They differed as to whether it is permissible to pray it after dawn. Some of them said it is not allowed, and others said that it is allowed so long as one has not yet prayed Fajr. The first view was expressed by Abu Yoosuf and Muhammad ibn al-Hasan, two companions of Abu Haneefah, and Sufyaan al-Thawri, and the second was expressed by al-Shaafa’i, Maalik and Ahmad. The reason for their difference of opinion was the actions of some of the Sahaabah which differed from what is mentioned in the reports.
My view concerning this matter is that what they did does not contradict the reports that have been narrated concerning that – I mean the reports which say that they allowed praying Witr after dawn. Rather they allowed it in cases where it needs to be made up, not as a regular practice. Their view would only contradict the reports if they said that this prayer could be offered after dawn on a regular basis. Think about it.
Bidaayat al-Mujtahid, 1/147, 148
Shaykh Ibn Baaz (may Allaah have mercy on him) said:
There are many ahaadeeth on this topic, which indicate that the time for witr ends when dawn begins.
Fataawa al-Shaykh Ibn Baaz, 11/306.