Deuteronomy 27:9

The ground of his exhortation is again taken from the special favor of adoption, wherewith the God of Abraham had honored them; for there was nothing which should have more effectually stimulated them to obedience, than that more than paternal love, and the gratuitous kindness with which He had prevented them. Although, at the same time, they were admonished in these words of the object for which they were separated from other nations; for the conclusion he draws is, that because they were received by God as His people, they, therefore, lay under an obligation to keep His statutes; as Paul more plainly teaches us that we are redeemed from all iniquity, that Christ might purify unto himself a peculiar people, zealous of good works. (Titus 2:14.) Moreover, since the priests were now appointed, from whose lips the doctrine of the law was to be sought, they here come forward in God’s own name, and engage the people to respond to His generous calls upon them; and not only this, but also to obey His ministers.