“Even people who believe in God cheat.”
It’s mutually exclusive. You can follow the bible, or you don’t. There is no “both”.
Believe in god I take to mean worship, in your context. Am I correct in that ? People who Believe don’t sin, unless they make honest mistakes and then repent. I believe it’s quite clear on this.
So if you perform a sin while thinking that God exists, You’re not a believer, or you’re not a sinner.
David cheated. He was a man after God’s own heart.
I’m not saying it’s right. Of course not!