Some interresting passages to ponder...
But what does it say? “The word is near you, in your mouth and in your heart” (that is, the word of faith which we preach): that if you confess with your mouth the Lord Jesus and believe in your heart that God has raised Him from the dead, you will be saved. (Rom 10:8)
and that every tongue should confess that Jesus Christ is Lord, to the glory of God the Father. (Php 2:11)
Therefore I said to you that you will die in your sins; for if you do not believe that I am He, you will die in your sins.” (Jn 8:24)
Then Jesus said to them, “When you lift up the Son of Man, then you will know that I am He, and that I do nothing of Myself; but as My Father taught Me, I speak these things. (Jn 8:28)
Jesus said to them, “Most assuredly, I say to you, before Abraham was, I AM.” (Jn 8:58)
And Thomas answered and said to Him, “My Lord and my God!” Jesus said to him, “Thomas, because you have seen Me, you have believed. Blessed are those who have not seen and yet have believed.” (Jn 20:28,29)
It was not only the resurrection of Jesus that Thomas believed, but that Jesus was his Lord and God. Jesus said, "if you do not believe that I am He, you will die in your sins." Jesus is God, the Son of God. That is essential.