When many speak of knowing Christ, they speak of the red letters of Matthew, Mark, Luke, and John. But Jesus is the creator of all, He's the Lord God almighty. The only savior. Jesus was present in the Old Testament portion of scripture, and Jesus had more to say from His ascended position in glory. When we are told that we no longer know Jesus after the flesh (2 Cor 5:16). We'd do well to consider what that means. Many know of Jesus after the flesh (as He was in Matthew, Mark, Luke, and John) rather than according to the revelation of the mystery of Christ.
"Now to him that is of power to stablish you according to my gospel, and the preaching of Jesus Christ, according to the revelation of the mystery, which was kept secret since the world began..." Romans 16:25 KJB