The old covenant was lacking until Jesus came. Its words about God were partial and incomplete. These words were shaped by men, trying to express to their contemporary culture what God was like and what He was saying. All fell short of knowing what the Father was really like until One came and said, “Whoever has seen me has seen the Father…The words that I say to you I do not speak on my own authority, but the Father who dwells in me does his works.” (Jn 14:9-10 ESV). The fullness of revelation and knowing God only comes in looking at Jesus.
“Long ago, at many times and in many ways, God spoke to our fathers by the prophets, but in these last days he has spoken to us by his Son, whom he appointed the heir of all things, through whom also he created the world.” Hebrews 1:1-2 (ESV)
