In the post titled "Dating" I cited 1 Corinthians 7:5 as justification for giving your all to your spouse, not withholding anything. I will mention it again, in the context of verses 3 and 4. (from the New Living Translation, so there is no ambiguity)
The husband should fulfill his wife’s sexual needs, and the wife should fulfill her husband’s needs. The wife gives authority over her body to her husband, and the husband gives authority over his body to his wife.
Do not deprive each other of sexual relations, unless you both agree to refrain from sexual intimacy for a limited time so you can give yourselves more completely to prayer. Afterward, you should come together again so that Satan won’t be able to tempt you because of your lack of self-control.
I love Kevin Lehman's summary of this verse from his "Making the Most of Marriage" study:
What the apostle Paul is telling married folks is 'do it.
Then pray together.
Then do it again.'
Some book, that Bible... I don't think I've ever heard a priest or pastor do a message based on this verse, and that's really too bad. The church has always shied away from discussing sex openly. Again, as Lehman said, "If there is anybody who should be talking about sex, it is the church!" But on the whole, we don't, and our world is the worse for it. In the absence of talk about its place in God's plan for marriage, we have let the world define its place in our culture and our lives. Sex is a gift from God, and it is meant to be enjoyed by husbands and wives. Married folks should claim it as their privilege to revel in each other's embrace without shame; indeed, with unabashed joy.
Like all gifts though, sex needs to be both given and received in the right spirit. As soon as it is seen as a "duty" it loses its magic. All other emotional and relational needs must be met and fulfilled before sex can take its rightful place. A Florida pastor challenged the married couples in his congregation to make love to each other every night for a month. Article here: http://www.cbsnews.com/stories/2008/02/20/earlyshow/living/relationships/main3850842.shtml
(A pastor in Texas issued a 7-day challenge; more modest, but in the same spirit) In light of all the other articles I've written, I’ll suggest that the real challenge here is not for the one spouse whose libido is lesser to "just do it" for the sake of the couple meeting the goal. The challenge is for the spouse whose libido is greater: can they be the partner (in all senses) that their spouse needs? Can they kindle desire in their spouse over and over? Can they be the someone their spouse wants to make love to every night for a week – or a month?
In one sense, sex in a marriage is akin to the good works the Bible tells us we are created for. (see Ephesians 2:10) Good works are not an end unto themselves, or the price of admittance into Heaven. What they are is the appropriate response to the love God has for His people.
Sex - passionate, fulfilling sex – is not a duty, or a bargaining chip, or a goal. It should be the joyous response to the love of your spouse.