Sahih Muslim 8933
In-book no 1656حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، قَالَ سَمِعْتُ عُقْبَةَ بْنَ حُرَيْثٍ، قَالَ سَمِعْتُ ابْنَ عُمَرَ، يُحَدِّثُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " صَلاَةُ اللَّيْلِ مَثْنَى مَثْنَى فَإِذَا رَأَيْتَ أَنَّ الصُّبْحَ يُدْرِكُكَ فَأَوْتِرْ بِوَاحِدَةٍ " . فَقِيلَ لاِبْنِ عُمَرَ مَا مَثْنَى مَثْنَى قَالَ أَنْ يُسَلِّمَ فِي كُلِّ رَكْعَتَيْنِ .
Ibn 'Umar reported Allah's Messenger (ﷺ) as saying: The night prayer consists of pairs and when you see the approach of dawn, make this number odd by one rak'ah. It was said to Ibn 'Umar: What does the (word) pair imply? He said: (It means) that salutation is uttered after every two rak'ahs.