MacArthur's notes on Genesis 9:25-27:

9:25-27 Cursed be Canaan. The shift from Ham to his son Canaan established the historic legitimacy of Israel’s later conquest of the Canaanites. These were the people with whom Israel had to do battle shortly after they first heard Moses’ reading of this passage. Here, God gave Israel the theological basis for the conquest of Canaan. The descendants of Ham had received a sentence of judgment for the sins of their progenitor. In 10:15-20, the descendants of Canaan are seen to be the earlier inhabitants of the land later promised to Abraham.

9:26 may Canaan be his servant. Conquered peoples were called servants, even if they were not household or private slaves. Shem, the ancestor of Israel, and the other “Semites” were to be the masters of Ham’s descendants, the Canaanites.The latter would give their land to the former.