Why does Paul quote from the Deuteronomy, the Psalms, and Isaiah when speaking about the promises given to the patriarchs?

The reference made to the promises given to the patriarchs creates a certain distance between Romans 5:8 and the quotations from Scripture that follow in Romans 15:9–12, for these all come from a later period in Israel’s history. However, the Greek text does not say patriarchon, which would be rightly translated as patriarchs, but rather pateron, i.e. fathers, as it is rightly translated in the KJV. Although Acts 2:29 also refers to David as a patriarchon, as a rule this term is restricted to the older generations of fathers mentioned in Genesis, namely the generations from Abraham to the twelve sons of Jacob (Acts 7:8–9, Hebrews 7:4). In contrast, the word pateron encompasses all those to whom the Word of God came in earlier centuries, including Moses and Isaiah, the prophet, who is quoted here in this passage.

Spreading the glory of the Lord among the Gentiles should therefore be understood as a confirmation (KJV) of the promises recorded in Scripture. Paul here uses the verb bebaiosai that does not specifically point to a later fulfilment like the Greek word pleosai does, but rather to the confirmation of a promise. In other words, the promise does not have to apply exclusively to the later time of Jesus’ earthly ministry, although it was of course then carried out in a most powerful manner. From the quotations Paul provides, it is apparent that he regards this perspective on the salvation of the Gentiles to have be present already in the time of David and of Moses.

The passages Paul quotes from Scripture specifically highlight the fact that the Gentiles will come to praise God. The first passage is from David’s final hymn of praise when he had finally been able to rest from all his enemies. God set him, as it were, on a pedestal in order to allow him to glorify God among the nations: Therefore I will praise you among the Gentiles and sing to your name (2 Samuel 22:50, see also Psalm 18:50). David here typified Christ who, following his resurrection from the dead, is able spread the glory of God among the nations through his apostles.

Moses too was already aware that God’s calling of his was a means to spread his glory among all nations, for the song known as the Song of Moses, which he had taught the people of Israel, contains the following line: Rejoice, O ye nations, with his people (Deuteronomy 32:43— KJV). The exodus out of Egypt did not go unnoticed among the nations. God already made his name known on earth during that time, and did so for a reason, namely that the nations together with Israel, would find joy with the Lord who killed Pharaoh and led his people out of Egypt.

Later, Israel was also taught to sing about this in the Psalms: Praise the Lord, all nations! Extoll him, all peoples! (Psalm 117:1). God always intended for his work in Israel to serve to establish his glory all over the whole world, and the fathers knew this very well. They experienced it when the Queen of Sheba visited, and with Naaman, with Ruth, and with all the proselytes. Psalm 87:1–7 proclaims the incorporation of people from all nations even in the time of the psalmist.

This same paradigm would also characterize the coming of the Redeemer: In that day the root of Jesse, who shall stand as a signal for the peoples—of him shall the nations inquire, and his resting place shall be glorious (Isaiah 11:10).¹