John Calvin on Deuteronomy 32:9

9 For the Lord’s portion is his people. This is the main point, that God was moved by nothing but His own good pleasure to make so much of this people, who had been derived from a common origin with all others: for when he says, that Jacob was the portion of Jehovah, and the lot of His inheritance, he does not mean that there was anything better in them than in others, but he assigns the reason why God preferred this one nation to the rest of mankind; viz., because He took it to Himself as His hereditary portion, which dignity depends upon His gratuitous election.