Marcionism
The teaching of the second century heretic Marcion, who made a distinction between what he believed was the inferior God of justice, the God of the Old Testament, who was the Creator and the God of the Jews, and the God of the New Testament, the Supreme God of goodness, of whom Christ was the messenger. Accordingly, he rejected the Old Testament; in fact, his canon included only Luke and Paul’s writings, which he edited to remove whatever he disagreed with, especially the quotes from the Old Testament found in them.

• From Marcionism and the New Mood (Kevin DeYoung):

Marcion’s theological errors (and there were many) came from one main root. He refused to believe that the God of the Old Testament was the same as the Father of the Lord Jesus Christ. Marcion could simply not believe in a God full of wrath and justice. So he threw away the Old Testament and took for his Bible a truncated version of Luke’s Gospel and selectively edited versions of Paul’s epistles. When all the cutting and pasting was finished, Marcion had the Christianity he wanted: a God of goodness and nothing else; a message of inspiring moral uplift; a Bible that does away with the uncomfortable bits about God’s wrath and hell. Marcionism was antinomian, idealistic about human potential, and skittish about dogma and rules.

• From Know Your Heretics: Marcion (Justin Holcomb):

Marcion’s heresy prompted the church to push back and officially recognize the Old Testament as Scripture. Furthermore, his rejection of the humanity of Jesus energized the church to develop a complete defense of it. Tertullian did exactly this in his work Against Marcion in 207-208. Tertullian saw Marcion’s denial of Christ’s humanity as detrimental to Christianity: “The sufferings of Christ will be found not to warrant faith in him. For he suffered nothing [if he] did not truly suffer; and a phantom could not truly suffer. God’s entire work therefore is subverted. Christ’s death, wherein lies the whole weight and fruit of the Christian name, is denied.”