I will make a new covenant... — Both in itself, and as the germ of the future of the spiritual history of mankind, the words are of immense significance. It was to this that the Lord Jesus directed the thoughts of His disciples, as the prophecy which, above all other prophecies, He had come to fulfil by the sacrifice of Himself. In that “New Covenant” in His blood, which He solemnly proclaimed at the Last Supper (Matthew 26:28), and which was commemorated whenever men met to partake of the Supper of the Lord (1 Corinthians 11:25), there was latent the whole argument of the writer of the Epistle to the Hebrews (Hebrews 8-10), the whole Gospel of justification by faith as proclaimed by St. Paul (Galatians 3:15-17). From it the Church took the title of the New Covenant, the New Testament, which it gave to the collected writings of the Apostolic age. This title in its turn gave the name of the Old Testament to the collected writings which recorded how “in sundry times and divers manners” God had spoken in time past to Israel.
The promise is too commonly dealt with as standing by itself, without reference to the sequence of thought in which we find it placed. That sequence, however, is not hard to trace. The common proverb about the sour grapes had set the prophet thinking on the laws of God’s dealings with men. He felt that something more was needed to restrain men from evil than the thought that they might be transmitting evil to their children’s children — something more even than the thought of direct personal responsibility, and of a perfectly righteous retribution. And that something was to be found in the idea of a law — not written on tablets of stone, not threatening and condemning from without, and denouncing punishment on the transgressors and their descendants, but written on heart and spirit (2 Corinthians 3:3-6). It is noticeable, as showing how like thoughts were working in the minds of the two prophets, that in Ezekiel also the promise of a “new heart and new spirit” comes in close sequence upon the protest against the adage about the “children’s teeth being set on edge” (Ezekiel 18:31). In the words for “saith the Lord” we have the more solemn word which carries with it the announcement as of an oracle from God.