How then can I do this great wickedness and sin against God? (Genesis 39:9)
When Potiphar’s wife made sexual advances toward Joseph, Joseph, by the grace of God, refused to give in to temptation. Even at one point, she clutched onto his robe, and he removed it and ran away. As he was refusing her the first time, one of the reasons he cites is that Potiphar had done no wrong to him, but his main issue was that it would be sin against God Himself. Joseph rightly acknowledged that sin against fellow man is ultimately sin against God.
David shared this sentiment as he mourned over his sin against Bathsheba and Uriah. He wrote, “Against you, you only, have I sinned and done what is evil in your sight” (Psalm 51:4). Surely David was aware of his adultery with Bathsheba and his conspiracy to murder Uriah. But his assessment is right: supremely, all sin is an affront to God.
For the believer, what that means is that when we sin against another, we should make ourselves right with that person, asking for their forgiveness. But we should also seek to restore our fellowship with the Lord (in the temporal sense). Any sin that we commit against a human is supremely against the very God who gave His only Son to forgive those sins for all eternity. It should grieve us to sin against others, because it is an act of ungratefulness for the grace that has been given to us.
For the unbeliever, what this means is that all the sins you’ve committed against others you’ve actually committed against the eternal God, and without an advocate, you are guilty of sin worthy of eternal punishment. But out of His unconditional love, He has sent His only Son to die on the cross and take on that punishment for sinners like you and me. So, turn to Jesus and trust in Him for total, irrevocable forgiveness. Against Him only have you sinned, and only through Him can you be forgiven.