From Sahih Muslim (Hadith 1766):
Jabir reported Allah's Messenger (ﷺ) as saying:If anyone is afraid that he may not get up in the latter part of the night, he should observe Witr in the first part of it; and if anyone is eager to get up in the last part of it, he should observe Witr at the end of the night, for prayer at the end of the night is witnessed (by the angels) and that is preferable
Reference: Muslim 1766