I read your sermon about masturbation, but I didn't find a Scripture that says it's wrong. Is it wrong to perform masturbation and petting? Is tongue kissing wrong? I am confused because does it mean that masturbation is a sin? Do you have any elders that you could ask? I am a member of the church of christ and I would really like to know.
Though I am not currently an elder, I have served as one in the past, and if the Lord is willing, I might have the opportunity to serve as an elder again in the future.
I don't know which article you have read. I've been asked about masturbation several times and answered it as closely as I can. "If anyone speaks, let him speak as the oracles of God" (I Peter 4:11). Most of the questions have come from men, but you indicate that you are female.
The Bible states, "as His divine power has given to us all things that pertain to life and godliness, through the knowledge of Him who called us by glory and virtue" (II Peter 1:3). God has told us everything we need to know to live life in a godly fashion, but it doesn't mean that every possibility has been laid out as a step-by-step set of rules. He has told us how to live life and when we run into a new situation, we must examine it to see if it is in accordance to what God has told us. "But examine everything carefully; hold fast to that which is good; abstain from every form of evil" (I Thessalonians 5:21-22).
Let me give you a more neutral example. Is eating sinful? At first you might think of course it isn't! But then we realize that overeating (gluttony) is wrong. Eating certain foods was also wrong if a person was raised in, say Judaism where eating pork was wrong, but now that they are a Christian they still are reluctant to eat pork. "Do you have faith? Have it to yourself before God. Happy is he who does not condemn himself in what he approves. But he who doubts is condemned if he eats, because he does not eat from faith; for whatever is not from faith is sin" (Romans 14:22-23). Even if you feel that eating something is not wrong, it can still be a sin if you eat something that causes a fellow Christian to stumble. "Therefore concerning the eating of things offered to idols, we know that an idol is nothing in the world, and that there is no other God but one. ... However, there is not in everyone that knowledge; for some, with consciousness of the idol, until now eat it as a thing offered to an idol; and their conscience, being weak, is defiled. But food does not commend us to God; for neither if we eat are we the better, nor if we do not eat are we the worse. But beware lest somehow this liberty of yours become a stumbling block to those who are weak. For if anyone sees you who have knowledge eating in an idol's temple, will not the conscience of him who is weak be emboldened to eat those things offered to idols? And because of your knowledge shall the weak brother perish, for whom Christ died?" (Romans 8:4, 7-11). What looks at first to be a simple matter becomes a bit more complex as we consider the impact of what we do upon ourself and upon others.
Is playing with your own genitals a sin? As you noted, there isn't a passage that we can go to that directly deals with the issue. Therefore, we look to see if related issues are a problem. It should be obvious that both in masturbation and petting there is a problem with sexual desire and thoughts. "For this is the will of God, your sanctification: that you should abstain from sexual immorality; that each of you should know how to possess his own vessel in sanctification and honor, not in passion of lust, like the Gentiles who do not know God; that no one should take advantage of and defraud his brother in this matter, because the Lord is the avenger of all such, as we also forewarned you and testified" (I Thessalonians 4:3-6). "Your vessel" is a reference to your physical body, being seen as a container for your spirit. Your body is to be used for honorable purposes as someone dedicated to God. In particular, Paul states it is not to be used for "passion of lust." That phrase comes from two Greek words which both refer to unlawful sexual lust. Your body was not given to you to be used to incite sexual passion in another person outside of marriage. Thus, petting would be wrong as it does just that, though it would be proper between a husband and wife (Proverbs 5:18-19; I Corinthians 7:3). Nor would it be proper to stimulate yourself and simultaneously fill your mind with thoughts of sexual acts with a person to whom you are not married. "But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart" (Matthew 5:28). Though this is addressed to men, the same principle would apply to women lusting after men.
I hope this makes things clearer in your mind.