Isaiah 56:3

The son of the stranger; the stranger, as the son of man is the same with the man, Isaiah 56:2; the Gentile, who by birth is a stranger to God, and to the commonwealth of Israel. That hath joined himself to the Lord; that hath turned from dumb idols to the living God, and to the true religion; for such shall be as acceptable to me as the Israelites themselves, and the partition-wall between Jews and Gentiles shall be taken down, and repentance and remission of sins shall be preached and offered to men of all nations. The eunuch; who is here joined with the stranger, because he was forbidden to enter into the congregation of the Lord, Deuteronomy 23:1, as the stranger was, and by his barrenness might seem no less than the stranger to be cast out of God's covenant, and cut off from his people, to whom the blessing of a numerous posterity was promised. And under these two instances he understands all those persons who either by birth, or by any ceremonial pollution, were excluded from the participation of church privileges; and so he throws open the door to all true believers, without any restriction whatsoever. A dry tree; a sapless and fruitless tree, accursed by God with the curse of barrenness, which being oft threatened as a curse, and being a matter of reproach among the Jews, might easily occasion such discouraging thoughts as are here expressed.