The concept of original sin was first alluded to in the 2nd century by Irenaeus, Bishop of Lyon in his controversy with certain dualist Gnostics.[4] Other church fathers such as Augustine also shaped and developed the doctrine,[5][2] seeing it as based on the New Testament teaching of Paul the Apostle (Romans 5:12–21 and 1 Corinthians 15:21-22) and the Old Testament verse of Psalms 51:5.[6][7][8][9][10] Tertullian, Cyprian, Ambrose and Ambrosiaster considered that humanity shares in Adam's sin, transmitted by human generation. Augustine's formulation of original sin after 412 CE was popular among Protestant reformers, such as Martin Luther and John Calvin, who equated original sin with concupiscence (or "hurtful desire"), affirming that it persisted even after baptism and completely destroyed freedom to do good. Before 412 CE, Augustine said that free will was weakened but not destroyed by original sin[2].