There are two passages in the New Testament that are often used to prove that same-sex relationships are wrong. They are 1 Corinthians 6:9-10 and 1 Timothy 1:10. Let’s have a look at 1 Corinthians.
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 Corinthians 6:9-10, NIV)
The word translated as male prostitutes is malakoi (singular: malakos), and the word translated as homosexual offenders is arsenokoitai (singular: arsenokoites). There is one, and only one, other place in the New Testament where arsenokoitai is used, and that is in 1 Timothy 1:10.
We also know that law is made not for the righteous but for lawbreakers and rebels, the ungodly and sinful, the unholy and irreligious; for those who kill their fathers or mothers, for murderers, for adulterers and perverts, for slave traders and liars and perjurers–and for whatever else is contrary to the sound doctrine (1 Timothy 1:10, NIV)
In this passage, it is translated as perverts. That’s a little odd. One word, used in essentially the same way, is translated as two completely different things in two passages in the same translation.
It gets odder when you look at different translations of those two passages. Consider the English Standard Version.
Do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor men who practice homosexuality, nor thieves, nor the greedy, nor drunkards, nor revilers, nor swindlers will inherit the kingdom of God. (1 Corinthians 6:9-10, ESV)
understanding this, that the law is not laid down for the just but for the lawless and disobedient, for the ungodly and sinners, for the unholy and profane, for those who strike their fathers and mothers, for murderers, the sexually immoral, men who practice homosexuality, enslavers, liars, perjurers, and whatever else is contrary to sound doctrine (1 Timothy 1:10, ESV)
The ESV has a footnote next to men who practice homosexuality that says “The two Greek terms translated by this phrase refer to the passive and active partners in consensual homosexual acts”. On the one hand, the translators of the ESV say that malakos and arsenokoites together mean men who practice homosexuality, but on the other they say just arsenokoites on its own means that. Once again, the translation of arsenokoites is not consistent between the two passages, but this time we can see that the translators of the ESV disagree with the translators of the NIV about what arsenokoites means. They also disagree about what malakos means. The NIV says it means male prostitutes but the ESV says it refers to one of the partners in consensual homosexual sex.
The third translation I’m going to mention is the New Jerusalem Bible.
Do you not realise that people who do evil will never inherit the Kingdom of God? Make no mistake – the sexually immoral, idolaters, adulterers, the self-indulgent, sodomites, thieves, misers, drunkards, slanderers and swindlers, none of these will inherit the kingdom of God. (1 Corinthians 6:9-10, NJB)
on the understanding that laws are not framed for people who are upright. On the contrary, they are for criminals and the insubordinate, for the irreligious and the wicked, for the sacrilegious and the godless; they are for people who kill their fathers or mothers and for murderers, for the promiscuous, homosexuals, kidnappers, for liars and for perjurers – and for everything else that is contrary to the sound teaching (1 Timothy 1:10, NJB)
The NJB is at least consistent with its translation of arsenokoites, rendering it as sodomites and homosexuals, but compare its translation of makakos to the others’: it has self-indulgent where the NIV has male prostitutes, and the ESV has the passive partner in homosexual acts. You cannot argue that those are in any way the same thing at all.
The translations of arsenokoites are just as bad. The NIV has homosexual offenders and perverts. The ESV isn’t clear about whether or not arsenokoites needs malakos to mean men who practice homosexuality, but even then the word perverts means something different from the phrase homosexual offenders, which in turn means something different from men who practice homosexuality, which in turn means something different from homosexuals and sodomites, which is what the NJB uses.
The truth of the matter is there is no consensus among Greek scholars about what the word arsenokoites means. If there was then there would be more consistency between translations. It is an obscure word, and nobody is really sure what it means. When someone quotes one of these passages as proof that the Bible says same-sex relationships are wrong, then they are on very shaky ground.
For more about the translation of arsenokoites and malakos, see Arsenokoités and Malakos: Meanings and Consequences by Dale B. Martin.