Answer:
I can see masturbating to porn is a sin. But sometimes i would think masturbating cant be bad for you when you go long periods without and your penis might start to itch. And what is better; ejaculate controlled, or do it in bed whole your asleep. The old semen has to get out some way. Please help me with this; is it a sin when not lusting for anything, but just masturbating for the pleasure and getting rid of old sperm cells?
Answer
Perhaps my answer to a previous question asking 'Do Christians masturbate?' might help:
Probably most Christians do masturbate, because they are human. In the Bible, the only reference to 'masturbation' is the case of Onan who was struck dead because he 'allowed his seed' to spill on the ground instead of impregnating his brother's wife. However, this case was more coitus interruptus (withdrawing the penis before ejaculation) than masturbation, and the punishent was given, not as a result of spilling his seed, but of refusing to obey the Law which compelled a brother of a dead husband to impregnate his wife so that the dead husband's line caried on through history.There is absolutely no other reference in scripture to anything even resembling masturbation. Jesus had precisely nothing to say on the matter.
There have, of course, been many incidents throughout history where the Church (and others, to be fair) have tried to prevent boys masturbating (of course, girls don't do it do they?;-) ) as they have decreed it sinful, self-abuse, and so on. Often they cite Paul's description of the human body as a 'Temple' of the Holy Spirit to back up their cause. But these cases have more to do with the Church leaders' own sexual hang-ups and sexual repression rather than Christianity as taught by Our Lord.
However, it is quite clear that God gave humans sexuality not only as a means to reproduce but also for pleasure. In the Song of Songs in the Old Testament, the poem tells allegorically of love practices between two lovers, and God sees it as good. In the right context of that loving monogamous relationship, reading between the lines of the poem, various sexual practices are described including oral sex and masturbation, and seem, by the nature of the poem, all to have God's blessing - provided they are in the right context.
Therefore masturbation is just a noral part of being human. Most Christians, both male and female will do it... some with a little shame because of a repressed background and of what they have been taught by equally repressed leaders, but most because it is simply a human need, given to us, presumably, by God himself.