Also the sons of the stranger, that join themselves to the LORD, to serve him, and to love the name of the LORD, to be his servants, every one that keepeth the sabbath from polluting it, and taketh hold of my covenant; The sons of the stranger - The Gentiles.
That join themselves to the Lord - Who shall enter into the Christian covenant by baptism and faith in Christ, as the Jews and proselytes did by circumcision.
To serve him - To live according to the Gospel, and ever do that which is right in the sight of the Lord.
To love the name of the Lord - The name of Jesus, the Christ, the Savior of sinners, the Anointed of God, and the Giver of the Holy Spirit to his followers.
To be his servants - To worship no other God but Jehovah, and to trust in none for salvation but his Christ.
That keepeth the Sabbath - That observes it as a type of the rest that remains for the people of God.
And taketh hold of my covenant - בבריתי biberithi, "of my covenant sacrifice;" as without this he can do nothing good; and without it nothing can be acceptable to the infinite majesty of the Most High.