Neither the Bible nor the Qur’an (Koran) has a lot to say about homosexuality, and what they do say relates only indirectly to contemporary discussions about gay rights and same-sex marriage. Like pre-modern scholars of law and ethics, these books assume heteronormativity.
As a concept, homosexuality is relatively recent, even if there is plenty of evidence for homoerotic pleasure in the past – albeit illicit in religious terms.
Scriptures and later writers usually referred only to particular sexual acts and did not raise the issue of personal sexual orientation. For religious conservatives, though, both Muslim and Christian, the occasional derogatory reference to same-sex acts is enough to prove their inherent sinfulness in all circumstances.
More liberal interpreters point to broader ethical considerations such as compassion and empathy. They argue that the condemnations of scripture do not apply to committed relationships founded on love.