﴿ إِنَّ رَبَّكَ هُوَ أَعْلَمُ مَن يَضِلُّ عَن سَبِيلِهِۦ ۖ وَهُوَ أَعْلَمُ بِٱلْمُهْتَدِينَ ﴾

“Verily, thy Sustainer knows best as to who strays from His path, and best knows He as to who are the right-guided.”

(Lo! thy Lord, He knoweth best who erreth from His way) from His religion and obedience; (and He knoweth best (who are) the rightly guided) to His religion, i.e. Muhammad (pbuh) and his Companions.