Luke 19:10 For the Son of Man has come to seek and to save that which was lost.
Jesus Christ Himself told us that the purpose of His coming to this earth was the salvation of man. Each person on earth is responsible to make sure His sacrifice was not in vain in that persons life.
John 3:1-18 And there was a man of the Pharisees named Nicodemus, a ruler of the Jews. He came to Jesus by night and said to Him, Rabbi, we know that you are a teacher come from God; for no man can do these miracles which you do unless God is with him. Jesus answered and said to him, Truly, truly, I say to you, Unless a man is born again, he cannot see the kingdom of God. Nicodemus said to Him, How can a man be born when he is old? Can he enter the second time into his mother’s womb and be born? Jesus answered, Truly, truly, I say to you, Unless a man is born of water and the Spirit, he cannot enter into the kingdom of God. That which is born of the flesh is flesh, and that which is born of the Spirit is spirit. Do not marvel that I said to you, You must be born again. The Spirit breathes where He desires, and you hear His voice, but you do not know from where He comes, and where He goes; so is everyone who is born of the Spirit. Nicodemus answered and said to Him, How can these things be? Jesus answered and said to him, Are you the teacher of Israel and do not know these things? Truly, truly, I say to you, We speak what we know and testify what we have seen. And you do not receive our witness. If I have told you earthly things and you do not believe, how shall you believe if I tell you heavenly things? And no one has ascended up to Heaven except He who came down from Heaven, the Son of Man who is in Heaven. But even as Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up, so that whosoever believes in Him should not perish, but have everlasting life. For God so loved the world that He gave His only-begotten Son, that whoever believes in Him should not perish but have everlasting life. For God did not send His Son into the world to condemn the world, but so that the world might be saved through Him. He who believes on Him is not condemned, but he who does not believe is condemned already, because he has not believed in the name of the only-begotten Son of God.
This is one of Jesus’ first references to salvation. Let’s look at it in detail. For one thing, we see the we absolutely must be born again of the water and the Spirit to enter the kingdom of God.
In verses 15 and 16 we see that belief is also fundamental to our salvation. Please note that unless believing somehow incorporates being born again of the water and spirit, we have a direct contradiction in the Word of God, and the Bible does not contradict itself.