John 20
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And many other signs truly did Jesus in the presence of his disciples, which are not written in this book: But these are written, that ye might believe that Jesus is the Christ, the Son of God; and that believing ye might have life through his name."
Read the rest of the book and count how many times the word believe (th, d) is used.
You'll have the answer if you use the King James Bible.
Heaven is by ...alone