Concise Bible Dictionary:
Twelve was God’s chosen number for Israel, under this number they were ever before Him, as manifested in the twelve stones on the breastplate and the twelve names on the two onyx stones in the shoulder pieces of the high priest, and in the twelve loaves on the table of shewbread. All these continued the same after the division of the ten tribes, and notwithstanding the separation. Though the ten tribes were dispersed, and as men think “lost,” Paul spoke of the twelve tribes constantly serving God in his day; and James addressed the twelve tribes in his epistle. In the New Jerusalem the names of the twelve tribes will be written on the twelve gates (Acts 26:7; James 1:1; Rev. 21:12). They remain ever twelve in God’s sight, as the church is ever one before Him.
In seven passages a list of the twelve tribes is given, but the order of the names varies in each, for which there is doubtless a divine reason. After Levi was separated for the priesthood, the number twelve was maintained by Ephraim and Manasseh being mentioned instead of Joseph. When Moses blessed the twelve tribes Simeon was omitted. The blessing there is not so much a prophecy of their historical future, as when Jacob blessed them, but according to their relationship with God in government and blessing. In Revelation 7, where the tribes are sealed for blessing, Dan is omitted, as being a type of Antichrist: Ephraim is also omitted, the number being made up by inserting Levi and by Joseph being mentioned as well as Manasseh. In the future division of the land Dan will have a portion, but will be the farthest from the temple (Ezek. 48:1-35). In the following table the names are numbered throughout according to birth. In Numbers 1 There are two lists of the tribes: one, the heads of the tribes, as given in the following table; the other, when the tribes were numbered, the only difference in the order of the names being that in the latter Gad comes before Judah.
In the accompanying map will be seen the situation of the tribes as the land was apportioned by Joshua. For the division of the land when the twelve tribes are restored by God, see the map under EZEKIEL.