The scripture is very clear about this issue,sex outside marriage is a sin, worse still every other sin is done outside the body but sex before marriage is done in the body and our body is meant to be the temple of the Holy Spirit and any one who defiles that temple will not be innocent before God. Sex is a commitment and should not be done indiscriminately. Lastly all adulterers, sexually perverse and fornicator will have his part in the lake of fire that burns with fire and brimstone. If you are guilty of such sin, repent now because God is merciful but his merciful nature should nnot be taken for granted.