Marcion of Pontus was a second century theologian who argued that the God portrayed in the Old Testament cannot be the same as the God proclaimed by Jesus. Marcion contrasted the cruelty, jealousy, and harsh justice of the God of the Old Testament with the God of pure mercy proclaimed by Jesus. Based on this understanding of Scripture, Marcion posited that the God of the Old Testament was the Creator God, but inferior and different from the God of mercy proclaimed by Jesus. . . To support this theology, Marcion created his own canon of Scripture, the first in Christian history. He rejected all the Old Testament, and accepted only Paul and Luke as genuine, but even these he modified by deleting certain passages.^^ Although Marcion died around 160, the church he founded persisted in the West until the end of the third century, and in the East until the middle of the fifth century.
Referred to by Polycarp as “the first born of Satan,” Marcion was one of the most famous heretics of the early church and the leader of the sect known as the “Marcionites.” Marcion is known for his Gnostic leanings which he integrated into a version of Christianity. . . Tertullian said that he was the first to separate between the Old Testament and the New Testament. This became known as the Marcion canon and served as a motivation for the church to deal more precisely with the issue of the canon of Scripture. Marcion was docetic with regard to be view of Christ, denying his full humanity. 
- ? Orlando O. Espin, James B. Nickoloff, An Introductory Dictionary of Theology and Religious Studies, Liturgical Press, 2007, s.v. Marcionism.
- Marcion: Portrait of a Heretic by Robert I Bradshaw.