Generally, adultery is still considered wrong in our culture – most people wouldn’t actively encourage someone to go and commit adultery. There is a recognition that the breaking of the significant promises made during marriage is neither loving or good. Most people will know someone who has been deeply affected by adultery and we can all see the wider impact on the communities we’re part of.
However, in the Bible, adultery isn’t a terrible wrong because of the pain it causes others but also because it’s an offence against God. In the Old Testament after King David has committed adultery he says, “Against you [God], you only, have I sinned and done what is evil in your sight,” (Psalm 51:4). I don’t think that David is saying he hasn’t wronged Bathsheba (with whom he committed adultery), nor Uriah (her husband) or anyone else involved. What he is acknowledging is that at its heart, adultery is despising God and His word (2 Samuel 12:9). There is a God-ward dimension to adultery which adds to the human pain and suffering it causes.
Secondly, adultery undermines the Gospel and misrepresents God. The unity that is found in marriage is supposed to be a very visual, lived out picture of the relationship between Christ and His church (Ephesians 5:25-33). The indissoluble union, the love, affection, faithfulness and submission that exists between Christ and the church should in some small way be reflected by marriage. A marriage marred by adultery paints a very different picture of the relationship between Jesus and the church. It paints a picture which calls into question everything that is good, comforting, joyful and secure between Jesus and the church.
The commandment to not commit adultery is, at root, a commandment to love other people and to love God, including representing God and the Gospel faithfully. Marriage lived in faithfulness to one another and to God is a wonderful testimony and picture of God’s faithfulness and love to his church.
For those who know their guilt in this area all too well, Psalm 51 continues with David calling God his salvation, deliverer and the one who can clean him. Adultery is serious, but not unforgivable. In his Psalm, David is crying out to God knowing that God will wash clean those who turn to Him in repentance and faith. David knows that even for those who have committed adultery, God will not despise a broken and contrite heart (Psalm 51:17) and we know there is always forgiveness at the foot of Jesus’ cross.