Genesis

Genesis 9:25 : Cursed (ארור) is Canaan: Noah said to Ham: "You caused me that I should not father a fourth son, another one to serve me. May your fourth son [Canaan was Ham's fourth son, see Genesis 10:6 ] be cursed by serving the offspring of these greater ones [of Shem and Japheth]... What did Ham see that he emasculated him? He said to his brothers Adam the first man had only two sons (Cain and Abel) yet one killed the other because of the inheritance of the world [Cain killed Abel over a dispute how to divide the world between them according to Genesis Rabbah 22:7] and our father has three sons yet he seeks still a fourth son." [30][31]

Genesis 9:26 : ...Blessed is יהוה the God of Shem: "Who is destined to keep His promise to [Shem's] offspring to give them the Land of Canaan" and he shall be: "Canaan shall be to them as a servant to pay tribute." [31][32]

Genesis 9:27 : and Canaan shall be a slave to them.: "Even after the children of Shem will be exiled slaves will be sold to them from the Children of Canaan." [Rashi explaining why the curse is repeated.] [30][31]