Romans 1:2 - Matthew Poole's English Annotations on the Holy Bible

Which he had promised; the meaning is not, that the history of the gospel was promised by the prophets, but that Jesus Christ, with all his benefits, (which is the direct subject of the gospel history and revelation), was promised or foreshown by them. Afore; this word is added to prevent the imputation of novelty: q.d. Let none object and say, the gospel is a new and modern doctrine; for it was promised or foretold of old, by all the prophets which have been since the world began, Luke 1:70. By his prophets: by prophets we may understand, not only those that were commonly dignified with that title, but all those also whom God condescended to converse with in a familiar manner, revealing his secrets to them: that such are called prophets, see Genesis 20:7 Psalms 105:15. In the holy Scriptures; to wit, of the Old Testament; he hath respect to the oracles and promises therein contained, concerning Christ and his kingdom; chiefly to Genesis 3:15, Genesis 49:8,10 Deu 18:18 Psalms 16:10 Psalms 22:1-31 40:1-17 110:1 Isaiah 7:14, Isaiah 9:6 53:1-12 63:1-3 Daniel 9:24-26 Micah 5:2 Malachi 9:9 Zechariah 3:1, &c. He hereby intimates, that there is a great harmony and consent betwixt the prophets and apostles, the doctrine of the Old Testament and the New; see Luke 24:44 1 Thessalonians 12:16 Acts 10:43. Our modern translators include this verse in a parenthesis; the ancients did not.