"God, after He spoke long ago to the fathers in the prophets in many portions and in many ways, in these last days has spoken to us in His Son" (Heb. 1:1-2).
A Samaritan woman declared, "I know that Messiah is coming (He who is called Christ); when that One comes, He will declare all things to us" (John 4:25). The expectation of that day, even among the Samaritans, was that Messiah would unfold the full and final revelation of God. The Holy Spirit, through the writer of Hebrews, affirms that to be true: "God . . . in these last days has spoken to us in His Son" (Heb. 1:1-2).
The Old Testament had given divine revelation in bits and pieces. Every piece was true, yet incomplete. But When Jesus came, the whole picture became clear, and though rejected by His own people, He was, in fact, the fulfillment of the messianic hope they had cherished for so many centuries.
The Old Testament age of promise ended when Jesus arrived. He is God's final word: "As many as may be the promises of God, in Him they are yes; wherefore also by Him is our Amen to the glory of God through us" (2 Cor. 1:20).
God fully expressed Himself in His Son. That's why John said, "The Word became flesh, and dwelt among us, and we beheld His glory, glory as of the only begotten from the Father, full of grace and truth. . . . No man has seen God at any time; the only begotten God, who is in the bosom of the Father, He has explained Him" (John 1:14, 18). Paul added that in Christ "all the fulness of Deity dwells in bodily form" (Col. 2:9).
The practical implications of that truth are staggering. Since Christ is the fullness of divine revelation, you need nothing more. In Him you have been made complete (Col. 2:10), and have been granted everything pertaining to life and godliness (2 Pet. 1:3). His Word is sufficient, needing no additions or amendments.