Muwaththa' Malik · #260
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يَقُولُ صَلاَةُ اللَّيْلِ وَالنَّهَارِ مَثْنَى مَثْنَى يُسَلِّمُ مِنْ كُلِّ رَكْعَتَيْنِ .
English
Yahya related to me from Malik that he had heard that Abdullah ibn Umar used to say, "(Voluntary) prayer in both the day and night is two at a time with a taslim after every 2 raka'ahs." Malik said, "That is the custom among us