Our Lord Jesus Christ is that Holy Ghost sent forth into all the earth. But just as the serpent deceived Eve by his craftiness, even so our minds have been corrupted from the simplicity that is in Christ. For the world have preached another Jesus whom the Apostles have not preached, and we have received a different spirit which the Apostles have not received, and a different gospel which the Apostle have not preached—and we have well put up with it! Take heed! For this is the testimony: that God has given us eternal life, and this life is in His Son. He who has the Son has life; he who does not have the Son of God does not have life. (1 John 5:11-12) And by this we know that the Son of God abides in us, by the Spirit whom He has given us. (1 John 3:24). For God have predestinated us unto the adoption of children by Jesus Christ to him. (Ephesians 1:5) And because you are sons, God has sent forth the Spirit of His Son into your hearts, crying out, “Abba, Father!” (Galatians 4:4-6). And we did not receive the spirit of bondage again to fear, but we received the Spirit of adoption by whom we cry out, “Abba, Father.” (Romans 8:15). Now if any man have not the Spirit of Christ, he is none of his. (Roman 8:9). But He that is joined unto the Lord Jesus Christ is One Spirit with the Lord (1 Corinthians 6:17). Because the Lord Jesus Christ is that Holy Ghost; and where the Spirit of the Lord is, there is liberty.( 2 Corinthians 3). A man must acknowledge and receive that Jesus Christ is that Holy Ghost to be saved.

Just as the children of Israel could not understand that Law of Moses. But their minds were blinded. Even so the world cannot understand the mystery of the gospel of Christ; which is Christ in you, the hope of glory. But even to this day, when the gospel is read, a veil lies on their heart. Nevertheless when one turns to the Lord Jesus Christ, the veil is taken away. Now the Lord Jesus Christ is the Spirit; and where the Spirit of the Lord is, there is liberty.( 2 Corinthians 3). Examine yourselves as to whether you are in the faith. Test yourselves. Do you not know yourselves, that Jesus Christ is in you?—unless indeed you are disqualified. (2 Corinthians 13:5). Now if any man have not the Spirit of Christ, he is none of his. (Roman 8:9). But He that is joined unto the Lord Jesus Christ is One Spirit with the Lord (1 Corinthians 6:17). For because you are sons, God has sent forth the Spirit of His Son into your hearts, crying out, “Abba, Father!” ( Galatians 4:6) and you did not receive the spirit of bondage again to fear, but you received the Spirit of adoption by whom we cry out, “Abba, Father.” (Romans 8:15). Today is the day of salvation, therefore believe the testimony of God and of Christ and of His apostles which said that God has given to us eternal life, and this life is in his Son. He that has the Son has life; and he that has not the Son of God has no life in him." (1 John 5:11-12) "And this is life eternal, that we might know Him the only true God, and Jesus Christ, whom God has sent. " (John 17:3).

And why should we believe any of this? if it's "bible said so" how does it become more believable than "Koran said so"?

the world is full of shiiit now than before the acclaimed jesus came.
whatever his mission was by whoever sent him is a total failure.