yes,
1 Corinthians 7:3-5
As for it being a sin... If you withhold sex because you want to manipulate your partner into something.. My personal opinion is that it's a form prostitution. You give them sex, If they give you what you want. I can't say for sure, But it sounds like prostitution. And since this ''prostitution'' isn't commited from a single woman to a man she doesn't know (or vice vera) but to their spouse in something as sacred as marriage, I could actually see God punishing this alot more harshly than ''real'' prostitution.
agreed. It is very much like prostitution in this regard.
@OP
I want to add that even if you are withholding because you just don't "feel" like it. that too is wrong. Paul says the husband's body belongs to his wife and hers to him.
If you disagree that, you are inviting powerful temptation into his/her life. You withholding is not an excuse to go commit adultery, but you are partly responsible because according to the Bible, it is a need that is a spouse's duty to fulfill. and if you refuse to fill that need, for whatever selfish motive, and some girl (or guy) out in the world is...
if your spouse is weak in that area he could fall into adultery. and you are partly responsible for causing his fall just like you would be if you caused an ex-alcoholic to start drinking again by bringing him to a bar or something.
Imagine if your husband was, for some reason, unable to cook and unable to learn to cook (not just too lazy to cook), and you decided to stop cooking for him. Sooner or later, he is going to find somewhere else to get food.
The same goes for every aspect of your relationship. If you start giving your spouse the silent treatment, chances are that your spouse is going to start talking to other people more. And depending on your spouse, your plan to withhold intimacy may backfire in a rip your life apart kind of way.
And this is not equivalent to rape. If you feel like you are being raped in fulfilling this responsibility to your spouse, you need counseling. because there are more serious issues going on than just "I don't feel like it".