Abu Zabyan (may Allah have mercy on him) narrated: We asked Sayyiduna Ibn Abbas (may Allah be pleased with them both): What is your view of the saying of Allah, the Mighty and Majestic: "Allah has not placed two hearts in any man's chest" [Al-Ahzab: 4]? He said: One day the Prophet of Allah (peace and blessings be upon him) stood up to pray, and a passing thought came to him (in the prayer). At this the hypocrites who were praying with him (peace and blessings be upon him) said: Do you not see that he has two hearts, one heart with you and one with them! So Allah, the Mighty and Majestic, revealed this verse: "Allah has not placed two hearts in any man's chest" [Al-Ahzab: 4].
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12557