Can masturbation be regarded as a sinful act?

The Bible does not explicitly mention masturbation, but it does provide principles regarding sexual purity and the thoughts and intentions of the heart. Jesus teaches that lustful thoughts are sinful, even if they do not lead to physical actions. Matthew 5:27-28 NKJV says, "You have heard that it was said to those of old, 'You shall not commit adultery.' But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart."

Masturbation often involves lustful thoughts or fantasies, which are considered sinful according to this passage. Additionally, 1 Corinthians 6:18-20 NKJV teaches that sexual immorality is a sin against one’s own body, which is the temple of the Holy Spirit: "Flee sexual immorality. Every sin that a man does is outside the body, but he who commits sexual immorality sins against his own body. Or do you not know that your body is the temple of the Holy Spirit who is in you, whom you have from God, and you are not your own? For you were bought at a price; therefore glorify God in your body and in your spirit, which are God’s."

While the Bible does not address masturbation directly, these principles about purity, self-control, and the sanctity of the body suggest that it is important to examine the motivations and thoughts associated with this act. If it leads to sinful thoughts, addiction, or hinders one's relationship with God, it should be avoided.