Twice he repeats that phrase you will “die in your sins.” Here Jesus does not use the singular word “SIN” but the plural word “SINS”. Here he is not directly referring to the sin of unbelief but that all of our sins condemn us, all of our sins separate us from God. And the only way to not die in our sins is to believe that Jesus IS who he says that he is—Jesus said, “I AM He” When God identified himself to Moses in Exodus chapter 3 he said, “I AM WHO I AM”; and God said to Moses “Thus you shall say to the sons of Israel, ‘I AM has sent me to you.'” I AM refers to God being an eternally, self-existing being. No one created Him, no one formed Him, no one was before Him and no one is above Him. And so Jesus is saying, “I am He” I was in the beginning with God and I am God. And salvation comes only through me—which is why he said, “Unless you believe that I am He, you will die in your sins.” Salvation comes through Jesus—and for everyone who dies—one of two things will happen to them when they die—they will either die with their sins still upon them and those sins will condemn them to hell or they will die with their sins forgiven because of their faith in Jesus Christ and they will be given eternal life.