The Scripture is strangely silent about this universal issue, while not shy about all sorts of other sexual situations and perversions... in great detail concerning sex with animals, etc. Yet the Bible says nothing about masturbation. This is odd, don't you think?
Some, mistakenly, cite Onan in Gen 38:9 as suggesting that masturbation is a sin. In fact, "onanism" has become a synonym for masturbation. But this is obviously an error, and a rather daft one at that. We know what Onan did, for it is spelled out for us in lurid detail; and we know why it was a sin: he was maliciously using and cheating Tamar in way that was wrong. In any case, what Onan was doing was certainly not
masturbating, and you have to be pretty dimwitted to miss this.
In fact, there is no place in scripture where masturbation is even mentioned, much less forbidden.