Mar 20, - The sin of Onan particularly was when he “spilled his seed on the ground” to avoid getting his brother's widow pregnant. This has been understood in the Church for two thousand years to refer to the sin of masturbation. The underlying premise here is that God gave us sex FOR ONLY ONE SITUATION AND TWO masturbation a sin according to Christianity? Jan 13, - The ends achieved by masturbation are not all that different than coitus . Onan's sin is most accurately interpreted as withdrawal, or coitus.