Why is having premarital sex considered immoral?

Answer 1

1 Thessalonians 4:3-8: “This is what God wills . . . that you abstain from fornication; that each one of you should know how to get possession of his own vessel in sanctification and honor, not in covetous sexual appetite such as also those nations have which do not know God; that no one go to the point of harming and encroach upon the rights of his brother in this matter, because Jehovah is one who exacts punishment for all these things, just as we told you beforehand and also gave you a thorough witness. For God called us, not with allowance for uncleanness, but in connection with sanctification. So, then, the man that shows disregard is disregarding, not man, but God, who puts his holy spirit in you.” (The Greek word por·nei′a, translated “fornication,” refers to sexual intercourse between unmarried persons, also to extramarital relations on the part of married persons.)

Eph. 5:5: “No fornicator or unclean person or greedy person—which means being an idolater—has any inheritance in the kingdom of the Christ and of God.” (This does not mean that anyone who in the past was a fornicator cannot enjoy the blessings of God’s Kingdom, but he must cease that way of life in order to have God’s approval. See 1 Corinthians 6:9-11.)

An authoritative answer to these questions can come only from our Creator—Jehovah God. And in his Word he tells us to “flee from fornication.” (1 Corinthians 6:18.) Just what does that mean? The Greek word translated “fornication” is not restricted to sexual intercourse but includes a variety of lewd acts. So if two unmarried people engage in oral sex or in fondling each others’ reproductive organs, they are guilty of fornication.

Answer 2

it may bring about children being born into an adverse situation or STDs. I even don't have any concern with pre-martial sex myself. only be secure and to blame and also you're reliable to pass.