Moses, the servant of the Lord, gave. Theodoret makes the tribes which received their inheritance through Moses the types of the believing Jews, and those who received it through Jesus (Joshua) the types of the believing Gentiles.
Reuben, Gad, and Manasseh were the first born of their respective mothers, and were thus types of the Jews, who were God's firstborn. As they passed over armed before their brethren, so we received the good tidings of salvation from the lips of Jews.
This is a characteristic specimen of the allegorical interpretation of the early fathers. But it will be observed that the children of Bilhah, who might have been selected more naturally than those of Zilpah, are entirely omitted.