Compare Joshua 8:32-35. The solemnity was apparently designed only for the single occasion on which it actually took place.
Deuteronomy 27:12, Deuteronomy 27:13
The tribes appointed to stand on Gerizim to bless the people all sprang from the two wives of Jacob, Leah and Rachel. All the four tribes which sprang from the handmaids Zilpah and Bilhah are located on Ebal. But in order, as it would seem, to effect an equal division, two tribes are added to the latter from the descendants of the wives, that of Reuben, probably because he forfeited his primogeniture Genesis 49:4; and of Zebulun, apparently because he was the youngest son of Leah.
The transaction presents itself as a solemn renewal of the covenant made by God with Abraham and Isaac, but more especially with Jacob and his family. Accordingly the genealogical basis of the “twelve patriarchs” (compare Acts 7:12; Revelation 7:4 ff), the sons of Jacob, is here assumed. The tribes of Ephraim and Manasseh are merged in the name of Joseph, their father; and Levi regains on this occasion his place collaterally with the others. “The Levites” of Deuteronomy 27:14 are no doubt “the priests the Levites” (compare Joshua 8:33), in whom the ministerial character attaching to the tribe was more particularly manifested. It is noteworthy that the group of tribes which stood on Gerizim far exceeded the other in numbers and in importance, thus perhaps indicating that even by the Law the blessing should at length prevail.
Deuteronomy 27:15
The “Amen” attested the conviction of the utterers that the sentences to which they responded were true, just, and certain; so in Numbers 5:22, and in our own Commination Office, which is modelled after this ordinance of Moses.
Deuteronomy 27:15-26
Twelve curses against transgressions of the covenant. The first eleven are directed against special sins which are selected by way of example, the last comprehensively sums up in general terms and condemns all and every offence against God‘s Law. Compare the marginal references.