Just as marriage symbolizes the unity and devotion between a man and woman, sex symbolizes the unity of the flesh as one. 

1 Corinthians 7:2 states, "But since sexual immorality is occurring, each man should have sexual relations with his own wife, and each woman with her own husband."

In addition, your body is a "temple of the Holy Spirit" (1 Corinthians 6:19) and therefore you should keep it pure and honor it. Verse 20 states that we should honor God with our bodies and being sexually immoral makes us unclean.

Before marriage, our focus should be on God, as that is the most important relationship in our lives at the time. After marriage, the Bible permits that we may focus on God and our spouse. God created sex not only for reproduction (Genesis 1:28), but also as a symbol of unity between a man and wife and something to be enjoyed within marriage (see the Song of Solomon 1:2-4, Ecclesiastes 9:9).

In conclusion, we must keep our bodies pure as they are temples for the Holy Spirit, honor God with our bodies, stay away from any sexual actions or thoughts before marriage, and keep sex as a symbolic unity between spouses and not as something to take lightly.