About the author
Abu Jafar Muhammad ibn Yaqub al-Kulayni (d.328/940 or 329/941) was born in the village of Kulayn in the city of Rayy, which today is nestled in the southern suburbs of Tehran, Iran. Because of his association with Rayy, he is sometimes referred to by the epithet al-Razi. Toward the end of his life, he gained the additional epithet of al-Silsili, since he lived near Darb al-Silsilah, one of the gates of Baghdad, which led toward Kufah. He has also been referred to as Abu Ja'far al-Awar ("the One-Eyed"), presumably because he had lost one of his eyes. It was not until many centuries later that Shaykh al-Baha'i began referring to him, in his book Miftah al-falah and in some of his letters of commendation (ijazah), as Thiqat al-Islam, which means "he upon whom Islam relies." Notwithstanding its late conferral, it is by this honorific title that he is now most commonly referred.
We do not know the specific year of his birth. However, by examining the dates when his teachers in Qum lived, and by assuming that he was between the ages of twenty and thirty when he studied with them, we can guess that he was born between 269/883 and 279/893.
He was from a family of scholars and transmitters of traditions. His maternal grandfather, Muhammad ibn Ibrahim al-Kulayni, was praised by Shaykh al-Tusi as being "praiseworthy." Shaykh al-Tusi also praised that maternal grandfather's brother, Ahmad ibn Ibrahim al-Kulayni, as being "praiseworthy," "an eminent scholar from the city of Rayy. Ali ibn Muhammad ibn Ibrahim al-Kulayni known as Allan al-Kulayni, was his maternal uncle and the most renowned scholar from this family until Shaykh al-Kulayni's time. Shaykh al-Najashi praised Allan al-Kulayni as being trustworthy and eminent. His book, Akhbar al-qaim, became one of Shaykh al-Kulayni's sources for al-Kafi.