To understand how this ‘masturbation is sinful’ idea came to be part of Christianity even up to today, you have to understand some history. So read on. This is fascinating and scary stuff. Around the time of Jesus some religious ideas, most likely originally from India, were arriving with traders and beginning to become popular in the countries around Israel, especially among the huge numbers of Greek-speaking people. The most important groups who adopted these ideas were the Stoic philosophers and a religious sect called the Gnostics.
One of their main teachings was that God had created only the spiritual world; the entire natural physical world, including human beings and their bodies, were created by Satan. They began to teach that the human body and its functions, especially its ‘sexual functions’ were totally evil, and tolerated only because there was no other way to produce children. For the first time masturbation was said to be evil, for two reasons: it ‘wasted one’s life force’, which they believed was limited in supply; and it was pleasurable. This was not what the Jews believed. Their Bible said that God had created everything, which of course included our sexual abilities. What’s more, Genesis 1v31 says, "God saw all that he had made and behold it was very good." So the Jews believed that sex was God’s idea and that within the sacred bond of marriage, where it found its fullest expression, it was to be celebrated and enjoyed.
Masturbation is not a sin. God provided masturbation for man. Physically stimulating one's self to orgasm in privacy is not a sin. God speaks of it in Leviticus 15:16. If you also read verse 18 the message is clear. God is speaking of two ways to have an orgasm: alone or with a woman. He compares them on an equal with each other. There is no sin offering specified for either one.
God connected uncleanness (social quarantine) with both ways of having an orgasm. This was not a punishment, but a way to encourage his people to do it at the right time of day. If it were done at the end of the day, followed with a bath, just before sunset, His people would gain the greatest benefit from the release of endorphins to promote better sleep and the uncleanness would be virtually null. By this timing method, God is allowing a person to have an orgasm as much as once a day without suffering any significant uncleanness. It also discourages a person from neglecting his sexual feelings until he has a wet dream that would make him unclean and quarantined for the whole next day. Paul supports the principle of frequent sexual attentions in 1 Cor. 7:5.
There is a concern though, in the New Testament Jesus warns about what is going on in the imagination. He stated that lusting for a woman in one's mind is adultery. So, thankfully enjoy the great sensations that God created into your sexual organs for you to delight in and let those great feelings bring you up to orgasm without imagining any forbidden relationships.
The idea is not to hurry things. Remember that God is the Creator of your sexual organs. He is the Great Physician. He can help you discover your body. That is why He turned on your hormones long before you are old enough to get married and have children. He would not have designed your body to start producing the hormones that create sexual desire so long before you should marry if He had intended sex to be for procreation only. He turned on your hormones early because He has provided a way for you to take care of them and intended for you to do so. In doing so, He also intends for you to discover how your body works and what will bring you the most pleasure. Your future wife should be doing the same thing, so when you are married, you can show each other the things that will bring you both the greatest delights. Proverbs 5:15-20 metaphorically tells us to satisfy our thirst for sex from our own fountain, not to do it with anyone else; then, when we marry, we may enjoy it to the fullest with our wife.
Remember, Satan can cause you to feel guilty. The Bible says he is the accuser of mankind. Wouldn't he want to make you feel guilty about masturbating so you would avoid it and have no escape from his temptations when your hormones built up? You bet! So, now you can send the Devil and his false guilt on his way with the assurance that God's Word has clearly provided for you to masturbate. This is what 1 Cor. 10:13 is speaking of, because without the provision of masturbation, man's hormones could drive him beyond his ability to resist the real temptation to commit sexual sin upon another person.