On the authority of Abū Dardāʾ (raḍi Allāhu ʿanhu), the Messenger of Allāh (صلى الله عليه وسلم) said:
“Will any of you fail to recite one-third of the Qurʾān nightly?” It was then said: “How can [we] recite one-third of the Qurʾān?” The Messenger of Allāh (صلى الله عليه وسلم) replied:
“Say: He is Allāh, (the) One.” [i.e. Sūrah al-Ikhlāṣ] is equivalent to one-third of the Qurʾān [Ṣaḥīḥ Muslim: 811].
Shaykh ʿAbd al-Razāq al-Badr mentions: Allāh is the greatest! What a tremendous virtue! Verily, there are 361,180 letters in the Qurʾān. It is said, there are 323,015 letters, and it is also said there are 340,740 letters in the Qurʾān, as mentioned by ibn Kathīr in the introduction of his tafsīr. If it were whoever recites a letter from the letters of the Qurʾān is rewarded with ten rewards as mentioned in the narration of ibn Masʿūd, then how many rewards would one attain if one recited the whole Qurʾān? [Keeping in mind] that reciting Sūrah al-Ikhlāṣ—being one line—three times is equivalent to that (of the whole Qurʾān). Allāh has made its reward great! This virtue does not mean that reciting (Sūrah al-Ikhlāṣ) three times will suffice you from reading the rest of the Qurʿān; rather, the salaf despised repeating its recitation more than once when reading (for khatm al-Qurʾān).
Source: Virtue of Sūrah al-Ikhlāṣ
Translated by: Munīb al-Ṣumālī