The prophet Isaiah foretold how Jesus died as our substitute. He died in the place of every believer, for our sins. It was prophesied centuries before it happened. "He was led as a lamb to the slaughter" (Isaiah 53:7). The Bible is such an amazing book. Inspired by the Holy Spirit, the Bible declares by the foreknowledge of God, how Christ died for us centuries before it was fulfilled.
Christ died as the Lamb of God, dying for the sins of the world. John the Baptist pointed to Jesus as the fulfillment of the prophecy. He said, "Behold! The Lamb of God who takes away the sin of the world" (John 1:29). He died to redeem believers out of all nations (Revelation 5:9). That is how Jesus died as our substitute.
Christ Jesus, like the passover lamb in the Old Testament, died in our place. He is every believer's substitute at the cross. He took your judgment and punishment. He shed his blood and poured out his life on your behalf. He died that believers may have life eternal. Our sin debt was paid in full by the Lamb of God.
Every believer can testify, that on the cross Jesus died in my place. Our testimony of faith is made sure by the Holy Spirit working grace in our hearts. By faith we see how Jesus died on the cross for us, knowing that he was the sacrifice for all of our sins (1 John 1:7).