The expectation of the godly: "The sun of righteousness shall rise"
to attest that he was Father, and to set apart for himself a chosen people. Hence, he was then surely known in the same image in which he with full splendor now appears to us. Accordingly, after Malachi has bidden the Jews heed the law of Moses, and continue in it earnestly because after his death there was to be an interruption of the prophetic office, he immediately afterward declares: “The sun of righteousness shall rise” [Malachi 4:2].
By these words he teaches that while the law serves to hold the godly in expectation of Christ’s coming, at his advent they should hope for far more light. For this reason, Peter says: “The prophets …searched and diligently inquired about this salvation,” which has now been made manifest by the gospel [1 Peter 1:10]. And “it was revealed to them that they were serving not themselves,” or their age, “but us, in the things which have …been announced” through the gospel [1 Peter 1:12].
Not that the teaching of these things was useless to the ancient people or without value for the prophets themselves, but because they did not come to possess that treasure which God has transmitted to us by their hand! For today the grace of which they bore witness is put before our very eyes. They had but a slight taste of it; we can more richly enjoy it. Accordingly, Christ declares that Moses bore witness to him [John 5:46], yet He extols the measure of grace in which we surpass the Jews. For he addresses his disciples: “Blessed are the eyes which see what you see; and blessed are the ears which hear what you hear. For many kings and prophets longed for this and did not attain it” [Luke 10:23-24; Matthew 13:16-17]. That God has preferred us to the holy patriarchs, who were men of rare piety, is no slight commendation of the gospel revelation." -- John Calvin, Institutes of the Christian Religion, v. 2, ch. 9