Although children are a natural result of sexual intercourse between a husband and wife and are called "a gift of the LORD" (Psalms 127:3 Psalms 127:3See, children are an heritage of the LORD: and the fruit of the womb is his reward.
American King James Version×, New American Standard Bible), the Bible does not prohibit sexual relations within marriage purely for pleasure. Indeed, it encourages such union.
The idea that sex was dirty and evil was an idea that crept into Christianity from early Catholic teachers. Their compromise with the obvious reality that sexual activity was necessary to have children resulted in their teaching that sex should only be engaged in by married couples when they wanted to have children. Yet there is no such instruction in the Bible.
Genesis 2:24 Genesis 2:24Therefore shall a man leave his father and his mother, and shall join to his wife: and they shall be one flesh.
American King James Version×says, "Therefore a man shall leave his father and mother and be joined to his wife, and they shall become one flesh [have sex]." Proverbs 5:15-19 Proverbs 5:15-19  Drink waters out of your own cistern, and running waters out of your own well.  Let your fountains be dispersed abroad, and rivers of waters in the streets.  Let them be only your own, and not strangers' with you.  Let your fountain be blessed: and rejoice with the wife of your youth.  Let her be as the loving hind and pleasant roe; let her breasts satisfy you at all times; and be you ravished always with her love.
American King James Version×encourages couples to enjoy sexual pleasure together within marriage. Paul says that husbands and wives should render the sexual affection due each other—refraining only during times set aside for prayer and fasting (1 Corinthians 7:3-5 1 Corinthians 7:3-5  Let the husband render to the wife due benevolence: and likewise also the wife to the husband.  The wife has not power of her own body, but the husband: and likewise also the husband has not power of his own body, but the wife.  Defraud you not one the other, except it be with consent for a time, that you may give yourselves to fasting and prayer; and come together again, that Satan tempt you not for your incontinency.
American King James Version×).
No passage in the Bible forbids husbands and wives from having sex for pleasure when not trying to conceive children. There is nothing wrong with couples using contraceptive methods, provided they are not physically harmful, to postpone having children until the time of their choosing.