“You shall not commit adultery.
‘In God’s order of priority, the sanctity of human life is followed by the importance of the marriage relationship…As a whole, the Bible reveals that God desires the establishment of harmonious marital relationships and that neither partner should do anything to undermine this.’ T.D.Alexander: ‘The New Bible Commentary’, p.108.
The Old Testament makes no distinction between crimes (committed against people) and sins (committed against God). In Amos 1:3-2:4 we find a long list of what we would call today ‘crimes against humanity’, but they are exposed as sins against the Lord, and He will punish. In Psalm 51:4, in view of his sins of adultery and murder, David can say to God, “Against you, you only, have I sinned.” We know he had sinned against Bathsheba, using his power and position to take her for himself; he had sinned against her husband, Uriah, by stealing his wife and having him killed, for no other reason than to cover his guilt (which, of course, he could not do).
According to Genesis 5:1,2, the image of God was reflected in the first man and woman, united in marriage. In their togetherness they bore the name “man”. So one of the things adultery does is to defile this image. God is the covenant-keeping God, but ‘Marital infidelity involves going back on one’s pledged word and therefore is a departure from the image of God.’ Alec Motyer: ‘The message of Exodus’, p.229. God is not like that. He is always faithful; He always keeps His Word.
It’s interesting that the next commandment is: “You shall not steal” because adultery is a form of theft, as already noted above.
Jesus had a very high standard for sexual behaviour. As in the case of murder, He was concerned with what was in a person’s heart (Matthew 5:27,28). Adultery is not only the act; it can also be in attitude.
‘Marriage,’ said the cynic, is like a besieged city: all those on the inside want to get out, and all those on the outside want to get in.’
Thankfully, that is not totally true, but there is some truth in there. What we can say is that marriage is under attack, and it behoves all of us who are married to guard our hearts, and seek God’s grace to be lovingly faithful in the marriages He has given us. The aim is that they may ‘preach the gospel’, and display to the world something of the wonder and beauty of Christ’s relationship with the church (see Ephesians 5:22-33).