You keep quoting a scripture about believing in Jesus Christ the Son of God and a secondary quote that faith comes by hearing about Jesus Christ. Cain knew nothing about the Son of God. Jesus was not born yet and wasnt going to be born for thousands of years. Cain didnt even know about a flood coming. Your interpretation makes no sense.
It would seem you are not mixing faith which is spoken of in Hebrew 4 (no gospel spiritual understanding ) in what we do hear or see coming from the word of God. And therefore believe God not seen .
In 2 Corinthians 4:18 there is a valuable tool needed to rightly divide the parables that do teach us how to walk by faith. The work of salvation was finished from the foundation of the world.it is from that work we ca rest being yoked with Christ.
The Son of God who remains without mother or father beginging of spirit life or end of it is our High Priest after the order of Melchezedek continually.
The Son of man, Jesus born of the corrupted flesh who came to demonstrate one time that work of his own flesh as that which the eyes see the temporal. Jesus declares it profits for nothing, zero. But rather it is the unseen spirit as the word of God that does quicken our souls giving us new spirit life.
2 Corinthians 4:18 While we look not at the things which are seen, but at the things which are not seen: for the things which are seen are temporal; but the things which are not seen are eternal.
Salvation does not depend of the birth of Christ as the Son of man in respect to his temporal flesh. But is considered the Son of God according to the unseen Holy Spirit of Christ with power according to unseen resurrection.
The same spirit of Christ that works in us that do believe to the salvation of our soul worked in Abel . God puts no difference between them and us... purifying their hearts by a work of His faith just as us. No power from the flesh, the demonstration
Romans 1:3-5 King James Version (KJV) Concerning his Son Jesus Christ our Lord, which was made of the seed of David according to the flesh; And declared to be the Son of God with power, according to the spirit of holiness, by the resurrection from the dead: By whom we have received grace and apostleship, for obedience to the faith among all nations, for his name:
No such thing as the flesh of holiness. We walk by faith, the eternal. . . not by sight. . the temporal.