Adam Clarke on Acts 15:11

Through the grace of the Lord Jesus Christ we shall be saved - This seems to be an answer to an objection, "Has not God designed to save us, the Jews, by an observance of the law; and them, the Gentiles, by the faith of the Gospel?" No: for we Jews can be saved no other way than through the grace of the Lord Jesus Christ; and this is the way in which the Gentiles in question have been saved. There is but one way of salvation for Jews and Gentiles, the grace, mercy, or favor coming by and through the Lord Jesus, the Christ; this is now fully opened to the Gentiles; and we believe we shall be saved in the same way.