Question: "What does the Bible say about birth control? Should Christians use birth control?"
Answer: The Bible does not address birth control or whether it is right for Christians to use birth control. Man was commissioned by God "to be fruitful and multiply" (Genesis 1:28) and marriage was instituted by God as a stable environment in which to have and rear children. In our society, children are often considered a nuisance and a burden. They can be seen as standing in the way of people's career paths, financial goals, or social freedom.
Genesis 38 tells of Judah's sons, Er and Onan. Er married a woman named Tamar, but he was wicked and the Lord killed him, leaving Tamar with no husband or children. Tamar was given in marriage to Er's brother, Onan, in accordance with the law of levirate marriage in Deuteronomy 25:5-6. Onan did not want to split his inheritance with any child that he might sire with Tamar on his brother's behalf, so he practiced the oldest form of birth control. Genesis 38:10 says "What he did was wicked in the Lord's sight; so He put him to death also." Onan's motivation was selfish: he used Tamar for his own pleasure, but refused to perform his “brotherly” duty of creating an heir for his deceased brother. This passage is often pointed to as evidence that God does not approve of birth control. However, it was not the act of contraception that caused the Lord to put Onan to death, but rather Onan’s selfish motives behind the action.
Here are some verses that describe children from God's perspective. Children are a gift from God (Genesis 4:1; Genesis 33:5). Children are a heritage from the Lord (Psalm 127:3-5). Children are a blessing from God (Luke 1:42). Children are a crown to the aged (Proverbs 17:6). God blesses barren women with children (Psalm 113:9; Genesis 21:1-3; 25:21-22; 30:1-2; 1 Samuel 1:6-8; Luke 1:7, 24-25). God forms children in the womb (Psalm 139:13-16). God knows children before their birth (Jeremiah 1:5; Galatians 1:15).
It is important to view children as God sees them, not as the world tells us we should. Having said that, the Bible does not forbid contraception. Contraception, by its definition, is the opposite of conception. It is not the act of contraception itself that determines whether it is wrong or right. As we learned from Onan, it is the motivation behind the contraception that determines if it is right or wrong. If a person is practicing contraception so they will have more for themselves, then it is wrong. If a person is practicing contraception in order to temporarily delay children until they are more mature and more financially and spiritually prepared, then it is acceptable to use contraception for a time. Again, it all comes back to motivation.
The Bible always presents having children as a good thing. The inability to have children is always presented in Scripture as a bad thing. At the same time, it cannot be argued from the Bible that it is explicitly wrong to use birth control for a time (please note that we are not referring to forms of birth control that function as abortifacients which end the life of the fetus. We are referring only to birth control methods that prevent fertilization). All married couples should seek the Lord’s will in regards to when and if they should try to have children and how many children they seek to have.