Well, after I said it was wrong for him to do it I did tell him he should talk to his male friends at church about it since he may get a better point of view from them. Since I don't want to be a nagging girlfriend. The thing is, I need to know if it's wrong to touch? and where it says in the bible about it.
I haven't read all the posts, so this is semi-blind.
The Bible doesn't directly address masturbation as far as I know. Some might disagree, though.
The Old Testament doesn't mention masturbation. I suppose some could say that is what was going on in the story of Onan. The Jews and the patriarchs had a custom, which would be written as law in the Law God gave to Moses. If a man died without descendants, his brother or close relative was to marry his widow and raise up a child in his name. Judah had a son who was wicked, so the Lord slew him. The young brother, Onan, took Tamar and was to 'raise up seed unto his brother' by having that first child with her.
Well, apparently Onan didn't mind having sex with Tamar, but he didn't want to have a child for his departed brother. So he spilled his seed on the ground. This was probably 'coitus interruptus' rather than masturbation. But who knows? It could have been both.
So in the middle ages, celibate priestly theologians developed a belief around this that masturbation was Onanism and that it was wrong for a man to spill his seed for non-reproductive purposes. The Bible doesn't directly teach this. It is derived from theological reasoning about passages like this and the purpose of sex in marriage.
This type of argument against masturbation is the same type of reasoning used in forbidden condoms and birth control in general. The Roman Catholic teaching relies heavily on church tradition, and so relies on this whole theological tradition related to the purpose of sex for their doctrine. Protestants tend to be 'scripture only' in their approach to such matters. Neither birth control nor masturbation are directly forbidden. So some Protestants are not against masturbation.
Now some Protestants are against masturbation for a number of reasons. Some people think it is impossible to touch without having lustful thoughts about another person. Other people disagree. I guess this could be a case of someone applying their own personal experience to others. There are numerous other arguments against masturbation.
Some people could view the practice as akin to a nocturnal emission, which wouldn't be sinful. Others see it more like a forbidden sex act.
I've encountered another line of reasoning against masturbation, too. The idea is that 'malakos' could refer to masturbators as well as certain homosexuals. I don't buy this, but it is one opinion that I have read.
In I Corinthians 6, Paul writes of a long list of sinners that they will not 'inherit the kingdom of God." There are two words there that are translated in a number of ways. The KJV says 'abusers of themselves with mankind' for the Greek arsenokoite and 'effeminite' for malakos.
Arsenokoite means 'man bedder.' It looks like the word might have been used because it is taken from words used in the Greek translation of that command not to lie with a man as one does with a woman. My guess is that this is a reference to that commandment from Leviticus.
The Grecco-Roman world distinguished in their thinking between the two types of participants in a homosexual act. The upper class free males, the virii of Rome, could do the arsenokoite thing and that could be considered, by some, to be somewhat socially acceptable. He could be the recipient of certain sexual acts, but not the giver of them. Lower status people, like slaves, could take the more servile role in these acts, but not the upper class person. It was considered degrading. We know both participants were sinning, but they probably didn't think of it that way.
Malakos is a bit more complicated. It has to do with being soft. I'll use the word 'softee' to refer to it. It can refer to the passive servile participate of a homosexual act, a catamite. But in Greek literature, it has a much broader use. A man could be called a 'softee' if he wore make-up or primped, or perhaps if he lacked discipline in certain areas. If a man plucked the hair out of his thighs, in one piece of literature, he would be considered a softee. (Of course, that could have been for homosexual purposes, too.) It seems like a lot of the uses had to do with things we would associate with being 'gay', but not everything.
Anyway, some have associated masturbating with being 'malakos'-- a softee. I am not sure if it was because this is something a catamite would do for an arsenokoite, and the logic is if he does it to himself, that's being a softee, too. Or maybe it has to do with the concept of a lack of sexual or moral discipline that comes with being a softee.
Whatever the case, in context, I am inclined to believe that Paul is talking about two types of homosexual behavior, especially since the Old Testament does not address the issue of masturbation as far as I know, or label it as sinful. I tend to view the 'fornication' restriction of Acts 15 as applying to sinful acts in Leviticus 18, for which Gentiles were driven out of the land, and ergo such actions are considered sinful for Gentiles. But if masturbation is not included among such sins, it would seem strange for Paul to suddenly spring that on everyone so unclearly in I Corinthians 6.