by Matt Slick

The whole point is that the nakedness, viewing the nakedness, the touching of the private areas, fondling, etc., are all reserved for the marriage bed between a husband and a wife. God clearly instructs that we remain morally pure.
1 Cor. 6:18, "Flee immorality. Every other sin that a man commits is outside the body, but the immoral man sins against his own body."
Eph. 5:3, "But do not let immorality or any impurity or greed even be named among you, as is proper among saints."
Col. 3:5, "Therefore consider the members of your earthly body as dead to immorality, impurity, passion, evil desire, and greed, which amounts to idolatry."
1 Thess. 4:2, "For you know what commandments we gave you by the authority of the Lord Jesus. 3 For this is the will of God, your sanctification; that is, that you abstain from sexual immorality; 4 that each of you know how to possess his own vessel in sanctification and honor, 5 not in lustful passion, like the Gentiles who do not know God."
Since intimacy before marriage involves the touching and often seeing of the naked body, this is an off-limits action. Save this for the proper context of marriage.