Al-Kāfi, vol. 2, no. 1

1. Ali ibn Ibrahim has narrated from his father from Hammad ibn ‘Isa from Rib’i ibn ‘Abd Allah from a man from Ali ibn al-Husayn (a.s.) who has said the following: “Allah, the Majestic, the Glorious, created the prophets from the clay of ‘Illiyiyyn (paradise), both their bodies and souls. He made the hearts of the believers from such clay and He made their bodies from a world lower than that world. He created the unbelievers, both their bodies and souls from the clay of Sijjin (fire). He thus mixed the two clays. For this reason children of unbelievers become believers and vice versa. For this reason the believers get afflicted with evil and unbelievers receive good things. Thus, the hearts of the believers incline to that from which they are created and the hearts of the unbelievers incline to that from which they are created.”