1 Corinthians 7:2 clearly includes sex before marriage in the definition of sexual immorality, all of the Bible verses that condemn sexual immorality as being sinful also condemn sex before marriage as sinful. Sex before marriage is included in the biblical definition of sexual immorality. There are numerous Scriptures that declare sex before marriage to be a sin (Acts 15:20; 1 Corinthians 5:1; 6:13, 18; 10:8; 2 Corinthians 12:21; Galatians 5:19; Ephesians 5:3; Colossians 3:5; 1 Thessalonians 4:3; Jude 7). The Bible promotes complete abstinence before marriage. Sex between a husband and his wife is the only form of sexual relations of which God approves (Hebrews 13:4).