Jesus interpreted the whole Old Testament as a commentary on Himself to the two disciples on the road to Emmaus. The writer of Hebrews begins his letter and keeps it going with the same effort; Jesus is the revelation of the Bible from Genesis to the end. He quotes the Old Testament over and over again and interprets it Christologically. He points out how it’s really about Christ. Some passages he uses are relatively obvious. But when he gets to Genesis 14 and the story of Abraham’s encounter with Melchizedek, he realizes that this is not so easy to understand. Understanding Jesus from Melchizedek is difficult to digest. So in Hebrews 5:12b-13 he says, “You need milk, not solid food, for everyone who lives on milk is unskilled in the word of righteousness, since he is a child.”
They should be teachers but they haven’t matured. What should they be teaching? They should be teaching as Jesus did to the two disciples on the road to Emmaus and what the writer of Hebrews demonstrates for them. They should be interpreting the Old Testament Christologically, that is, as it pertains to Jesus of Nazareth as the Messiah. This is what the author of Hebrews has been doing all along and this is what Christian expositors of the Bible should do as well. If it’s “Christian,” it must be about Christ or even better, Jesus as the Christ. The writer moves on from the milk of the Psalms and other obvious passages about the Messiah and reaches back to Genesis 14 and the story of Melchizedek. But that’s solid food. They are not ready for that yet because of their immaturity. He argues that just drinking the milk, although nourishing when you’re a child, will not foster true maturity. Milk keeps one “unskilled in the word of righteousness.”
Commentators are divided over what “the word of righteousness” means. Some suggest it is referring to our own personal righteousness. But the Bible makes it clear (Isaiah 64:6) that all of “our righteous deeds are as filthy rags” to God. The New Testament (Romans 3:10) says “there is none righteous no not one!” Paul tells the Philippians that he’s not trusting in his own personal righteousness but in Jesus. He writes in Philippians 3:9, “…not having a righteousness of my own that comes from the law, but that which comes through faith in Christ, the righteousness from God that depends on faith.” Jesus is the “word” of righteousness. Jeremiah actually told the sinful nation that righteousness would be theirs but not through good works. Jeremiah 33:15-16 says, “In those days and at that time I will cause a righteous Branch to spring up for David, and he shall execute justice and righteousness in the land. In those days Judah will be saved, and Jerusalem will dwell securely. And this is the name by which it will be called: ‘The LORD is our righteousness.’”