where can i find a scripture that teaches this doctrine requirement for salvation?
Hebrews 11:6 But without faith it is impossible to please him: for
he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him.
John 8:24 "I said therefore unto you, that
ye shall die in your sins: for if ye believe not that I am he, ye shall die in your sins."
The word "he" is in italics (John 8:24) which means it isn't in the original. Unless you believe "I am" (Ego eimi), you shall die in your sins. So what is Jesus saying?
Exodus 3:14 And God said unto Moses, I AM THAT I AM: and he said, Thus shalt thou say unto the children of Israel, I AM hath sent me unto you.
Jesus is saying He is the "I AM" of Exodus 3:14 that only applies to God.
This is the basic teaching. The teaching for the Trinity is also in scripture and who God is.
Acts 5:3 But Peter said, Ananias, why hath Satan filled thine heart to lie to the Holy Ghost, and to keep back part of the price of the land?
Acts 5:4 Whiles it remained, was it not thine own? and after it was sold, was it not in thine own power? why hast thou conceived this thing in thine heart? thou hast not lied unto men, but unto God.
Acts 5:3-4 basically says the Holy Spirit is God.
Ephesians calls God our Father:
Ephesians 1:2 Grace be to you, and peace, from
God our Father, and from the Lord Jesus Christ.
John 1:1 Says the Word is God.
Colossians 2:9 says in him (Jesus) dwells the fulness of the Godhead bodily:
Colossians 2:9 For in him dwelleth all the fulness of the Godhead bodily.
There are a lot more verses but the Bible calls the Father God, the Son (Jesus) God, and the Holy Spirit God.
The Biblical term is the Godhead and the common term for this is the Trinity.
So when Hebrews says that those who come to him must believe that He is, who is He? Whom do you have to believe that He is?
Hebrews 11:6 But without faith it is impossible to please him: for
he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him.