"I committed adultery. That broke my covenant, so why would God honor His with me?"
How it sounds in your head: I was unfaithful to my wife in my fifties. I broke the most sacred covenant I had. If I couldn't keep my vow to her, how can I expect God to keep His vow to me? Covenant-breakers don't get covenant blessings.
"Thus God, determining to show more abundantly to the heirs of promise the immutability of His counsel, confirmed it by an oath, that by two immutable things, in which it is impossible for God to lie, we might have strong consolation."
-- Hebrews 6:17-18Source: Religion teaching reciprocal covenant instead of the one-sided covenant of grace where God swears by Himself.
The parallel seems logical—he broke a sacred vow, so God can break His. The shame of adultery carries decades of weight, and at life's end, it feels like disqualifying evidence that he's not covenant-worthy. Marriage is called a picture of Christ and the church, so destroying it seems to void the spiritual reality.
David committed adultery with Bathsheba, murdered her husband Uriah to cover it up, and lied about it for months. The moment he confessed, Nathan said, 'The LORD has put away your sin; you shall not die'—INSTANT forgiveness, no probation, and David remained king and in the Messianic line.
I REFUSE the lie that my broken covenant voids God's! IT IS WRITTEN: God confirmed His covenant by an oath to HIMSELF—not to my performance. It is IMPOSSIBLE for God to lie, and His oath is IMMUTABLE. David committed adultery AND murder and heard 'your sin is put away' INSTANTLY! IT IS WRITTEN: there is NO condemnation for those in Christ Jesus. The BARAK blessing doesn't depend on my faithfulness—it depends on God's unchanging nature. I stand in COMPLETE forgiveness and full covenant blessing RIGHT NOW!
God didn't wait for you to prove yourself faithful before making the covenant—He entered it KNOWING every way you'd fail, and He bound Himself to it by His own blood. Your adultery was already factored into the price Jesus paid; it doesn't surprise Him or change His oath.