The Bible does not mention masturbation or state whether or not masturbation is a sin. The passage most frequently associated with masturbation is the story of Onan in Genesis 38:9–10. Some interpret this passage to say that “spilling your seed” is a sin. However, that is not what the passage is saying. God condemned Onan not for “spilling his seed” but because Onan was rebellious. Onan refused to fulfill his duty to provide an heir for his deceased brother. The passage is not about masturbation but about fulfilling a family obligation.
A second passage sometimes used as evidence that masturbation is a sin is Matthew 5:27–30. Jesus speaks against having lustful thoughts and then says, “If your right hand causes you to sin, cut it off and throw it away.” While there is clearly a connection between lustful thoughts and masturbation, it is unlikely that Jesus was alluding to the specific sin of masturbation in this passage.
The Bible nowhere explicitly states that masturbation is a sin, but there is no question that the actions that usually lead to masturbation are sinful. Masturbation is nearly always the result of lustful thoughts, inappropriate sexual stimulation, and/or pornography. It is these problems that need to be dealt with. If the sins of lust, immoral thoughts, and pornography are forsaken and overcome, masturbation will become much less of an issue and temptation. Many people struggle with guilt concerning masturbation, when, in reality, they would be far better off repenting of the sins that lead them to masturbate.