It was narrated from Jabir that the Messenger of Allah ﷺ said:
“Whoever among you fears that he will not wake up at the end of the night, let him pray Witr at the beginning of the night, then go to sleep. Whoever hopes that he will wake up at the end of the night, let him pray Witr at the end of the night, for recitation (of the Qur’an) at the end of the night is attended (by the angels), and that is better.”

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ سَعِيدٍ، حَدَّثَنَا ابْنُ أَبِي غَنِيَّةَ، حَدَّثَنَا الأَعْمَشُ، عَنْ أَبِي سُفْيَانَ، عَنْ جَابِرٍ، عَنْ رَسُولِ اللَّهِ ـ ﷺ ـ قَالَ " مَنْ خَافَ مِنْكُمْ أَنْ لاَ يَسْتَيْقِظَ مِنْ آخِرِ اللَّيْلِ فَلْيُوتِرْ مِنْ أَوَّلِ اللَّيْلِ ثُمَّ لْيَرْقُدْ وَمَنْ طَمِعَ مِنْكُمْ أَنْ يَسْتَيْقِظَ مِنْ آخِرِ اللَّيْلِ فَلْيُوتِرْ مِنْ آخِرِ اللَّيْلِ فَإِنَّ قِرَاءَةَ آخِرِ اللَّيْلِ مَحْضُورَةٌ وَذَلِكَ أَفْضَلُ " .