And that the Gentiles ... - The benefits of the gospel were not to be confined to “the Jews;” and as God “designed” that those benefits should be extended to the “Gentiles,” so the Jewish converts ought to be willing to admit them and treat them as brethren. That God “did” design this, the apostle proceeds to show.
Might glorify God - Might “praise,” or give thanks to God. This implies that the favor shown to them was a “great” favor.
For his mercy - Greek, On account of the mercy shown to them.
As it is written - Psalms 18:49. The expression there is one of David’s. He says that he will praise God for his mercies “among” the pagan, or when surrounded “by” the pagan; or that he would confess and acknowledge the mercies of God to him, as we should say, “to all the world.” The apostle, however, uses it in this sense, that the “Gentiles” would “participate” with the Jew in offering praise to God, or that they would be united. This does not appear to have been the original design of David in the psalm, but the “words” express the idea of the apostle.
And sing ... - Celebrate thy praise. This supposes that “benefits” would be conferred on them, for which they would celebrate his goodness.