“The Messenger of Allah ﷺ said: ‘The covenant that distinguishes between us and them is prayer; so whoever leaves it, he has committed Kufr.’” (Using translation from Ibn Mājah 1079)
قَالَ رَسُولُ اللهِ ﷺ بَيْنَنَا وَبَيْنَهُمْ تَرْكُ الصَّلَاةِ فَمَنْ تَرَكَهَا فَقَدْ كَفَرَ