James Haldane (1768 – 1851) was converted later in life and entered the ministry as a Scottish Presbyterian. Upon further study, he and his brother became baptists. Through their evangelistic efforts they planted many churches in the area. Historian Nick Needham gives an overview of their lives here.
James was not shy about his baptist beliefs. In addition to writing “Reasons of a Change of Sentiment & Practice on the Subject of Baptism,” he also wrote a commentary on Galatians titled “An Exposition of the Epistle to the Galatians, Showing That the Present Divisions Among Christians Originate in Blending the Ordinances of the Old and New Covenants” (1848).
(He also began writing a commentary on Hebrews, which was published posthumously from his manuscripts).
Haldane says that each of the Abrahamic promises “received a literal and a spiritual fulfillment.” For example, he notes that the promise
that God would be a God to him and to his seed after him… had its fulfilment in the riches and prosperity of Abraham, and in Israel after the flesh, being brought into covenant with God; whereby he became their God, and acknowledged them as his peculiar people. Its spiritual fulfilment was, God becoming God of the true Israel, – Abraham’s children by faith, – by a better covenant, established upon better promises.
One great means by which Satan has succeeded in corrupting the Gospel has been the blending of the literal and spiritual fulfilment of these promises, – thus confounding the old and new covenants. The former was a type of the latter, and to this the Apostle refers, in speaking of the revelation of the mystery ‘which was kept secret since the world began, but now is made manifest, and by the Scriptures of the prophets, according to the commandment of the everlasting God, made known to all nations for the obedience of faith’ (Rom 6:26). The mystery here spoken of is, the hidden meaning of God’s dealings with the posterity of Abraham, to which, in his epistles, Paul frequently refers.