Okay, time for the truth!
No, masturbation is NOT a sin and nowhere in the bible is masturbation even discussed at all. All of that is based on man made superstitions about masturbating being evil and leading to all sorts of diseases, insanity, blindness, homosexuality, etc. It's all made up.
The commonly accepted "biblical" scripture which states "It is better to cast your seed in the belly of a whore than to spill it on the ground", is not even in the bible! No book, chapter or verse in the bible says that. That was just made up by religious zealots who wanted to scare people into thinking that God would punish them for masturbating.
Another scripture from the bible that people like to bring up to try to discourage people from masturbating is the story of Onan, who God punished because he "spilled his seed on the ground". But what they don't tell you is that Onan wasn't masturbating at the time, he was having sex with his dead brothers wife, then pulled out "spilling his seed on the ground". He actually disobayed God and that's why he was punished, not for masturbating.
Every sin (and more specifically every sexual sin) is clearly spelled out in the bible (fornication, adultery, incest, homosexuality, bestiality) and nowhere does it include masturbation. Why would God specifically call all those other things sins then conveniently leave out masturbation, unless it was never meant to be a sin at all. That proves that it is totally acceptable.
Most Christian denomonations no longer teach that masturbation is sinful, but there are a few that still do. Catholics still believe it is a sin because they feel that anything done sexually other than for reproduction is wrong (even though that is not supported in the bible at all). A few other Christian groups believe that masturbation is sinful because "lust" is a sin and they feel that if you masturbate then you must be lusting at the time (even though that's not necessarily true). But whatever your opinion is on the matter, the bible doesn't say that masturbation is a sin and everyone does it. God gave all of us that instinct and since masturbation is the only form of safe sex and is considered healthy for you to do, as a Christian I have no problem sleeping like a baby after I masturbate. Hope that clears it up for you.
Coolmike disagree's with me, and that's fine because he is entitled to his opinion. But opinion is not fact and let's just get the facts straight here: The bible is very clear on what the sins are (sexual and non sexual). There is no ambiguity at all! Everything that is sinful in the bible is mentioned. Masturbation is not. If God truly wanted to consider masturbation a sin he would have said point blank "though shall not masturbate" or words to that effect. It's a natural biological instinct that everyone has (even animals). Only PEOPLE (specifically religious fanatics who were probably undercover perverts) decided that masturbation was a sin and only in the last few centuries. Lust is a sin in the bible, but masturbation is not. You can masturbate without lusting and there is nothing immoral about it. People eat, drink, use the bathroom and watch TV several times a day too. Does that mean they are putting those things above God? Did God say that you can only do other things so many times a day or that you have to worship him so many times a day? NO. What commandment does masturbation disobey? That is a question that Coolmike won't be able to answer because there is no such commandment.