John Calvin’s (1509-1564) enthusiasm for the word of God is clear as his interpretation of this passage meditates on the value of Scripture and its role in the Christian life. He defends the value of both Old and New Testaments for the edification of believers, arguing that as the same Spirit of Christ oversaw the composition of both, and so both carry the teaching of the Lord.
For everything that was written in the past was written to teach us, so that through the endurance taught in the Scriptures and the encouragement they provide we might have hope.
Commentary on Romans 15:4
This is a wondrous passage. For by it we know that nothing contained in the oracles of God is vain and unfruitful. We also learn at the same time that by reading Scripture we progress in piety and purity of life. Therefore whatever has been handed down in Scripture we should take pains to learn. For it would be to insult the Holy Spirit if we imagine that he has taught anything that is unimportant for us to know. So whatever is taught in Scripture, we should know, tends toward progress in piety. Although he’s talking about the Old Testament, nevertheless the same thing should be understood about the apostolic Scriptures too. For if Christ’s Spirit is the same everywhere, there is no doubt that now through the apostles, as formerly through the prophets, he has accommodated his teaching for the edification of his people. Moreover, here the fanatical spirits who crow that the Old Testament has been abolished and that it does not apply to Christians whatsoever are quite rightly proved to be liars. For by what audacity will they rob Christians of those things that, Paul testifies, have been appointed by God for their salvation?
Romans 9–16, eds. Philip D. W. Krey and Peter D.S. Krey, Reformation Commentary on Scripture, NT Vol. VIII, 210.