Sunan an-Nasa'i 463
It was narrated from 'Abdullah bin Buraidah that his father said:
"The Messenger of Allah (ﷺ) said: 'The covenant that stands between us and them is the Salah; whoever abandons it, he has committed disbelief.'"
أَخْبَرَنَا الْحُسَيْنُ بْنُ حُرَيْثٍ، قَالَ أَنْبَأَنَا الْفَضْلُ بْنُ مُوسَى، عَنِ الْحُسَيْنِ بْنِ وَاقِدٍ، عَنْ عَبْدِ اللَّهِ بْنِ بُرَيْدَةَ، عَنْ أَبِيهِ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏
"‏ إِنَّ الْعَهْدَ الَّذِي بَيْنَنَا وَبَيْنَهُمُ الصَّلاَةُ فَمَنْ تَرَكَهَا فَقَدْ كَفَرَ ‏"‏ ‏.‏