Is it permissible to delay the Witr prayer until just before the Fajr prayer?

Scholars have agreed that the time for Witr begins after the 'Isha prayer and ends at the break of dawn (Fajr), based on the Prophet's (peace be upon him) saying: "Witr is before dawn," and "Whoever reaches dawn and has not prayed Witr, there is no Witr for him." This is evidence that praying Witr after its optional time has passed, by the entry of Fajr, is not legislated.

However, for one who forgot Witr or slept through it, it is legislated for him to pray it when he wakes up or remembers it, based on his (peace be upon him) saying: "Whoever slept through Witr or forgot it, let him pray it when he wakes up or remembers."

The preferred time for Witr is between the 'Isha prayer and the break of dawn, based on his (peace be upon him) saying: "The night prayer is two rak'ahs by two rak'ahs, and if any of you fears the coming of dawn, he should pray one rak'ah which will make odd what he has already prayed," and "Witr is between the 'Isha prayer and the break of dawn."

A Muslim should be diligent in performing Witr at its appointed time, and whoever misses Witr at night should make it up as an even number of rak'ahs during the day, from after sunrise until just before zawal (midday).