“The writer of Hebrews makes a distinction between the message of the Old Testament prophets and that of Jesus: “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. . .” (Hebrews 1:1–2, NASB).
Literally, the Greek does not say in His Son, but it says in a Son. God’s message in the New Testament differed from His message in the Old Testament—not only in content, but also in the channel through which it came. In the Old Testament, God spoke through prophets in the New Testament, He spoke through a Son. Only Jesus as a Son could reveal God as Father.”