John Gills Exposition of the Bible Commentary - Deuteronomy 27:20
Cursed be he that lieth with his father's wife ,.... As Reuben did, and which is forbidden Leviticus 18:8 , because he uncovereth his father's skirt ; see Deuteronomy 22:30 , and all the people shall say Amen ; the tribe of Reuben said this as well as the rest. read more
Matthew Henry's Complete Commentary - Deuteronomy 27:11-26
When the law was written, to be seen and read by all men, the sanctions of it were to be published, which, to complete the solemnity of their covenanting with God, they were deliberately to declare their approbation of. This they were before directed to do (Deut. 11:29, 30), and therefore the appointment here begins somewhat abruptly, Deut. 27:12. There were, it seems, in Canaan, that part of it which afterwards fell to the lot of Ephraim (Joshua's tribe), two mountains that lay near together,... read more