عن ابن مسعود رضي الله عنه قال: قال رسول الله صلى الله عليه وسلم : «مَنْ قَرَأ حَرْفاً مِنْ كِتاب الله فَلَهُ حَسَنَة، والحَسَنَة بِعَشْرِ أمْثَالِها، لا أقول: ألم حَرفٌ، ولكِنْ: ألِفٌ حَرْفٌ، ولاَمٌ حَرْفٌ، ومِيمٌ حَرْفٌ».
[صحيح] - [رواه الترمذي]
Ibn Mas‘ūd (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: "Whoever recites a letter from the Book of Allah will be credited with a good deed, and the good deed receives a ten-fold reward. I am not saying that “ألم” Alif-Lām-Mīm is one letter, but Alif is a letter, Lām is a letter and Mīm is a letter."
Sahih/Authentic. - [At-Tirmidhi]
Ibn Mas‘ūd (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) explained that any Muslim who reads a letter from the Book of Allah (the Qur’an) will be rewarded with ten good deeds for each single letter. He did not consider “ألم” (Alif-Lām-Mīm) to be one letter, but rather Alif is a single letter, Lām another letter, and Mīm is a third letter. So anyone who recites this three-letter word is rewarded with thirty good deeds. This, indeed, is a great blessing and a magnanimous reward. Therefore, a Muslim should increase his recitation of the Book of Allah, the Exalted.