Imam Ja‘far al-Ṣadiq (as): Every single heart has two ears; at one of them stands a guiding angel, and at the other stands a deceiving devil. One commands him and the other prevents him; the devil commands him to sin and the angel prevents him from it, and that is the meaning of Allah's verse in the Quran: "When the two receivers receive, sitting on the right and on the left. Man does not utter any word except that with him is an observer prepared [to record]." al-Kāfī