Gilles Quispel

After finishing secondary school in Dordrecht, Quispel studied classical philology from 1934 to 1941 at the Leiden University.

Quispel completed his doctoral work in 1943 at Utrecht University with a dissertation examining the sources utilized in Tertullian's Adversus Marcionem.

Quispel served as a visiting professor at Harvard University in 1964-1965 and at the Katholieke Universiteit Leuven in 1968.

Quispel also made contributions to the study of early "Jewish-Christian" traditions as well as Tatian's Diatessaron (a second-century gospel harmony).

This book including unpublished essays, such as an important paper on Jesus in Islam, in which he argued that the origin of most of the Islamic sayings of Jesus were from Judeo-Christian / Jewish Christian sources (as opposed to Gentile Christians).