WHEN THE SINGLE UNIT OF PRAYER IS BEST H 1161 "Whosoever fears that he might not be able to get up in the latter part of the night should offer his Witr (one unit of) prayer during the early part of the night, but whosoever is eager to get up in the latter part should offer his Witr prayer at that time because during the latter part of the night it is attended (by the angels) and prayer at that time is best." R 1161 Muslim with a chain up to Jabir who related that the Messenger of Allah, praise and peace be upon him, said this.
1138- وعن جابر رضي الله عنه ، قَالَ : قَالَ رسولُ الله صلى الله عليه وآله وسلم : "مَنْ خَافَ أنْ لاَ يَقُومَ مِنْ آخِرِ اللَّيْلِ ، فَلْيُوتِرْ أوَّلَهُ ، وَمَنْ طَمِعَ أنْ يَقُومَ آخِرَهُ فَلْيُوتِرْ آخِرَ اللَّيلِ ، فَإنَّ صَلاَةَ آخِرِ اللَّيْلِ مَشْهُودَةٌ ، وذَلِكَ أفْضَلُ" رواه مسلم .