Thanks for your question.
The Bible is completely silent on the subject of masturbation. It neither condones nor condemns the practice. Any conclusion on the matter is of necessity an extrapolation from what the Bible teaches about sexual morality. God makes clear that sexual activity is acceptable to him only within marriage between a man and a woman.
Hebrews 13:4 Marriage is honourable in all, and the bed undefiled: but whoremongers and adulterers God will judge.
NKJV 1Corinthians 6:18 Flee sexual immorality. Every sin that a man does is outside the body, but he who commits sexual immorality sins against his own body.
Christ teaches that sexual immorality begins in the mind.
Matthew 5:28 But I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart.
Under the Law of Moses, ejaculation made a man ceremonially unclean.
Leviticus 15:16 And if any man’s seed of copulation go out from him, then he shall wash all his flesh in water, and be unclean until the even.
It was not that ejaculation itself is unclean, because it is a natural process designed by God, but rather that it symbolised ‘that which cometh out of a man’ which Christ clearly explains.
Mark 7: 20 And he said, That which cometh out of the man, that defileth the man.
21 For from within, out of the heart of men, proceed evil thoughts, adulteries, fornications, murders,
22 Thefts, covetousness, wickedness, deceit, lasciviousness, an evil eye, blasphemy, pride, foolishness:
23 All these evil things come from within, and defile the man.
The problem with masturbation is that it is almost of necessity accompanied with what may be classed as lascivious if not adulterous thoughts.
Here we are in a ‘grey’ area because ‘thought’ is not ‘deed’.
James 1:14 But every man is tempted, when he is drawn away of his own lust, and enticed.
15 Then when lust hath conceived, it bringeth forth sin: and sin, when it is finished, bringeth forth death.
16 Do not err, my beloved brethren.
The ideal is that our thoughts should be otherwise engaged.
Philippians 4:8 Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good report; if there be any virtue, and if there be any praise, think on these things.
We cannot be governed by what another man thinks, we have to read the scriptures and decide for ourselves what we allow.
Romans 14:5...Let every man be fully persuaded in his own mind.
22 ... Happy is he that condemneth not himself in that thing which he alloweth.
23 ...for whatsoever is not of faith is sin.
Paul experienced the problem of doing that which he didn’t allow within himself (I am not implying that Paul had a problem with masturbation).
Romans 7:15 For that which I do I allow not: for what I would, that do I not; but what I hate, that do I.
24 O wretched man that I am! who shall deliver me from the body of this death?
25 I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin.
We are not supermen/women, we all have weaknesses. We might decide a man’s penis and semen are under his own control before marriage. Upon marriage they belong to his wife.
NKJV 1Corinthians 7:4 The wife does not have authority over her own body, but the husband does. And likewise the husband does not have authority over his own body, but the wife does.
If we decide masturbation is wrong, but we still can’t help ourselves, then we have an advocate with the Father.
1John 2:1 My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous:
1John 1:9 If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
I hope this helps