What does the Bible say about birth control? This is my first question here! I'm Christian and I've read the Bible for a while, but I haven't seen anything related to birth control.

I know that Paul says that husband and wife can agree to refrain from sexual intercourse for a while, whenever it is for dedicating more time to pray. But I don't know something more specific. On the other hand, God calls us to sexual purity, so I'm a bit confused about it.
But Onan knew that the child would not be his; so whenever he slept with his brother's wife, he spilled his semen on the ground to keep from providing offspring for his brother.&quot;
Genesis 38:9 - New International Version (©2011)

This is the scripture I think of when birth control is brought up. Onan's brother had died so his brother's wife came to belong to him (as was the custom then). He wasted his sperm though and God killed him for what he had done.
Children are a gift from God and were particularly seen as such in the Bible times (for instance barren women would be miserable and pray for offspring). Purposefully remaining childless while in a married relationship is something apparently common today, but not exactly natural.

If people are fighting and hit a pregnant woman and she gives birth prematurely but there is no serious injury, the offender must be fined whatever the woman's husband demands and the court allows. But if there is serious injury, you are to take life for life
Exodus 21:22,23

The unborn are alive and seen by God as individuals - here causing the death of one carried the death penalty as for murder. They carry the potential to grow, as does every human, and have that potential right from the moment they were conceived (even before, as sperm).
Therefore the only form of &quot;birth control&quot; that I would see as Biblically OK is abstinence. If you really do not want children then it is best to stay single, as Paul advised.