A certain distinguished Prophet here announces himself as having deep secrets to open (Psa. 78:1-2). A company of Prophets then, according to divine appointment and by way of admonition, trace the history of God’s ways in grace, and Israel’s ways in perverseness, from the Exodus to David (Psa. 78:3-72).
Thus we have “things new and old,”—the new being the secrets just hinted at by the speaker of the two first verses, the old being the well known things rehearsed by the company of Jewish prophets.
Now we know that the Lord Jesus Christ took the place of this distinguished Prophet—this Prophet of new things, and so, in measure, does every one instructed in the kingdom of heaven (Matt. 13:35,52). In such sense the least there is greater than John the Baptist. St. Paul was eminently among these instructed scribes, being conscious that he was bringing forth the new things (see 1 Cor. 2; Eph. 3; Col. 1), things kept secret, or hidden mysteries. And no scribe is duly instructed in the kingdom of heaven, or a due teacher in the present dispensation, who does not discern between the things “new and old.”
But the old things as well as the new are of grace. The difference is rather in the old being Jewish or earthly, the new being of the Church or heavenly. (John 3:12.) This is the difference. But the old or Jewish things of this Psalm very distinctly tell of final grace and salvation. For Israel is here recorded to have destroyed themselves, and God at the last to have arisen in the grace that could set up David, and choose Zion and Judah for their help and recovery. And so will it be in the latter day. They are now a scattered and judged people again, having again destroyed themselves; but again they will be gathered and blest under the true David, the true King of Zion, the true Lion of Judah. And in the integrity of a heart that never can swerve, and in the skilfulness of a hand that never can err, He will keep and feed His Jewish flock on their native mountains.
NOTE—I would suggest that a full stop ought to he put to Psalm 78:2 and that Psalm 78:3-4 ought to be read thus: “That which we have heard and known, and our fathers have told us, we will not hide from their children.”