Summary: The gay marriage debate has become a contentious issue on the national scene. The intensity of arguments against gay marriage is matched, and sometimes surpassed, by the emotionally charged arguments for same-sex marriage. The Bible, however, is very clear on the subject and leaves no doubt about God's position. [2015 edit:] The U.S. Supreme Court's June 26, 2015, decision legalizing gay marriage in all 50 states is in opposition to the clear teaching of Scripture. I encourage all believers to hold to the truths of Scriptures in the face of ever-changing societal moral perspectives.
2) The public health catastrophe among homosexual men.
3) Numerous studies showing the importance to children of a father and a mother.
•• But today let’s look at biblical arguments against gay marriages.
• These Scriptures may be of no interest to unbelievers or to those who believe that courts and legislatures are the official definers of morality.
• But these are the biblical reasons that should drive us to hold to the Word of God and to resist approving of same-sex marriage.
1 Corinthians 6:9 Do you not know that the wicked will not inherit the kingdom of God? Do not be deceived: Neither the sexually immoral nor idolaters nor adulterers nor male prostitutes nor homosexual offenders nor thieves nor the greedy nor drunkards nor slanderers nor swindlers will inherit the kingdom of God.
(1) God defines homosexual offenders as among “the wicked.”
• Ephesians 5:11, KJV And have no fellowship with the unfruitful works of darkness, but rather reprove them.
• The Christian’s duty is to reprove, not to ignore, that which God calls wicked.
(2) God lists “homosexual offenders” among those who He determines will “not inherit the kingdom of God.”
• No “tolerance” there. No bowing at the altar of “diversity” there.
• No endorsement from heaven of homosexual churches.
• No platitudes about the love of God embracing all lifestyles and behaviors, including homosexual marriages.
Genesis 13:13 Now the men of Sodom were wicked and were sinning greatly against the Lord.
Genesis 19:4-5, 11-13, 24 Before they had gone to bed, all the men from every part of the city of Sodom — both young and old — surrounded the house.  They called to Lot, “Where are the men who came to you tonight? Bring them out to us so that we can have sex with them.” ...  Then [the messengers from God] struck the men who were at the door of the house, young and old, with blindness so that they could not find the door.  The two men said to Lot, “Do you have anyone else here — sons-in-law, sons or daughters, or anyone else in the city who belongs to you? Get them out of here,  because we are going to destroy this place. The outcry to the LORD against its people is so great that He has sent us to destroy it.” ...  Then the LORD rained down burning sulfur on Sodom and Gomorrah — from the LORD out of the heavens.
(3) Homosexuality incurred God’s destructive judgment upon an entire city.
• Rampant homosexuality was a major contributor to the decline and fall of the Roman Empire.
• It may be that San Francisco has not yet been judged because of the God-fearing Christians living there among the sodomites.
(4) The men of Sodom were said to be “sinning greatly” because of their men having sex with men.
• Other sins of Sodom are listed in Scripture, but this is the one that the Bible features as their great sin — the one that incurred God's wrath against their city.
• Bible-believing Christians cannot just look the other way and say that same-sex marriage is simply a “personal choice.” Not when God defines the participants in homosexual conduct as "sinning greatly".
• Christians cannot fall for the modern mantra that it’s not our business what people choose to do “behind closed doors”. The biblical arguments against gay marriage do not leave Bible believers the option of simply ignoring conduct that God is seen to have judged severely in the Bible record.
• God specifically says that homosexual conduct is “sinning greatly,” and Jesus came to save us from our sins.
Jude 1:7 In a similar way, Sodom and Gomorrah and the surrounding towns gave themselves up to sexual immorality and perversion. They serve as an example of those who suffer the punishment of eternal fire.
(5) God labels Sodom’s sin as “sexual perversion.”
• Societies (again, ancient Rome) that remain in perversion are doomed — Remember Sodom!
Romans 1:18, 24-28, 32 The wrath of God is being revealed from heaven against all the godlessness and wickedness of men who suppress the truth by their wickedness....  Therefore God gave them over in the sinful desires of their hearts to sexual impurity for the degrading of their bodies with one another.  They exchanged the truth of God for a lie, and worshiped and served created things rather than the Creator — who is forever praised. Amen.  Because of this, God gave them over to shameful lusts. Even their women exchanged natural relations for unnatural ones.  In the same way the men also abandoned natural relations with women and were inflamed with lust for one another. Men committed indecent acts with other men, and received in themselves the due penalty for their perversion.  Furthermore, since they did not think it worthwhile to retain the knowledge of God, he gave them over to a depraved mind, to do what ought not to be done....  Although they know God’s righteous decree that those who do such things deserve death, they not only continue to do these very things but also approve of those who practice them.
(6) God’s Word identifies husband-wife relations as “natural relations” and homosexual relations as “unnatural ones.” God defines same-sex marriages, therefore, as "unnatural" relationships.
• Again (27) God calls this “perversion” that receives a “due penalty.”
(7) God’s word also condemns “approving of those who practice [homosexuality].”
• That is why we need judges and legislators who will show their disapproval of same-sex marriage and will rule and legislate against gay marriages. Tragically in America today, [2015 edit] gay marriage bans properly passed by state legislatures have been overturned at the Supreme Court by judges whose legal decision has set them in direct contradiction to God's clear position on this.
Matthew 19:4-5 “Haven’t you read,” [Jesus] replied, “that at the beginning the Creator ‘made them male and female,’  and said, ‘For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh’?
(8) Jesus resolved the gay marriage debate once and for all — God made them “male and female ... a man ... [and] his wife". I see this as one of the most compelling biblical arguments against homosexual marriage and for traditional marriage. Jesus Christ Himself referred back to the biblical creation account and confirmed God's intent that marriage is designed by Him to be between a man and a woman. This Scripture portion is a crystal-clear revelation of what God says about marriage as He defines it.
1 Corinthians 6:11, KJV And such were some of you: but ye are washed, but ye are sanctified, but ye are justified in the name of the Lord Jesus, and by the Spirit of our God.
•• There is hope and forgiveness for all sins and all sinners who will repent and come to Jesus.
Summary of Biblical Arguments Against Gay Marriage
1. God lists “homosexual offenders” among “the wicked” (1 Corinthians 6:9).
2. God lists “homosexual offenders” among those who He determines will “not inherit the kingdom of God” (1 Corinthians 6:9).
3. Historically, homosexual conduct has incurred God’s destructive wrath upon an entire city (Gen. 19:4-5, 11-13).
4. God’s word defines the men of Sodom as “sinning greatly” because of their men having sex with men (Genesis 13:13; 19:5).
5. God calls Sodom’s sin “sexual perversion” (Jude 1:7). Societies that remain in perversion (Sodom, Rome ... the USA?) are on the road to destruction.
6. God’s word identifies husband-wife relations as “natural relations” and homosexual relations as “unnatural ones” (Romans 1:26-27) and “perversion” (vs. 27).
7. God’s word also rebukes those who “approve of those who practice” homosexuality (Romans 1:32). That should serve as a strong warning from God to our judges and legislators who decide cases and pass laws permitting same sex marriages.
8. Jesus settled the marriage issue once for all, declaring that God had made them “male and female ... a man ... [and] his wife” (Matthew 19:4-5). Jesus' affirmation of the heterosexual definition of marriage left no room for same-sex marriages.