"I heard 'Abdullah bin Mas'ud saying: 'The Messenger of Allah ﷺ said: "[Whoever recites a letter] from Allah's Book, then he receives the reward from it, and the reward of ten the like of it. I do not say that Alif Lam Mim is a letter, but Alif is a letter, Lam is a letter and Mim is a letter."
قَالَ رَسُولُ اللَّهِ ﷺ مَنْ قَرَأَ حَرْفًا مِنْ كِتَابِ اللَّهِ فَلَهُ بِهِ حَسَنَةٌ وَالْحَسَنَةُ بِعَشْرِ أَمْثَالِهَا لاَ أَقُولُ الم حَرْفٌ وَلَكِنْ أَلِفٌ حَرْفٌ وَلاَمٌ حَرْفٌ وَمِيمٌ حَرْفٌ