The Prophet ﷺ said: He who separates from the community within a span takes off the noose of Islam from his neck. (Using translation from Abū Dāʾūd 4758)
قَالَ رَسُولُ اللَّهِ ﷺ «مَنْ فَارَقَ الْجَمَاعَةَ قِيدَ شِبْرٍ فَقَدْ خَلَعَ رِبْقَةَ الْإِسْلَامِ مِنْ عُنُقِهِ»