13 Thus saith the Lord GOD; This shall be the border, whereby ye shall inherit the land according to the twelve tribes of Israel: Joseph shall have two portions.
(Verse 13, 14) Thus says the Lord God: This is the boundary in which you shall possess the land according to the twelve tribes of Israel, for Joseph has a double portion. Each of you shall possess it equally as his brother, to whom I raised my hand to give it to your fathers; and this land shall fall to you as a possession. Because we said that Joseph has a double portion, the Septuagint translated it as an increase of the portion. For indeed Joseph is interpreted as increase; understanding the matter instead of the name, and confusing the mind of the reader. For when the Levite tribe was subtracted and delegated to temple sacrifices, there remained eleven tribes, of which the tribe of Joseph was divided into two, Ephraim and Manasseh, who said to Joshua the son of Nun: Why have you given me the possession of one lot and one portion, since I am of such a great multitude, and the Lord has blessed me? To which Joshua responded: If you are a large population, go up into the forest and clear for yourself the spaces in the land of the Perizzites and Rephaim, because the possession of the mountain of Ephraim is narrow for you (Joshua 17: 14, 15). And again, Joshua said to the house of Ephraim and Manasseh: You are a large and powerful people, you shall not have one portion, but you shall go to the mountain and clear for yourself spaces to dwell, and you will be able to advance further when you have driven out the Canaanite, who you say has iron chariots and is strongest (Ibid., 27). We say this for the following reason: because the Scriptures now mention Joseph, that is, Ephraim and Manasseh, as having a double portion. But each tribe, according to its own multitude, receives equal portions of land, not divided by the will of the divider, but by lot, which is in the power of the Lord. Finally, even Joshua himself, who was the divider of the land, did not separate for himself a particular piece of land, so as not to appear to have chosen the best; but he received from the leaders of all the tribes, Timnath-serah in the mount of Ephraim.
[AD 420] Jerome on Ezekiel 47:13-14