Hi, my promise is in 1 Corinthians 15:56-57 which says, “The sting of death is sin, and the power of sin is the law. But thanks be to God! He gives us the victory through our Lord Jesus Christ.”
So the promise is, that God has given us the “win” by Jesus. Also in those verses it says to give thanks to God, which means that when we pray we should also give Him thanks for giving us the victory, because we wouldn’t be able to do it without Him.