Sforno on Genesis 9:26/ספורנו על בראשית ט׳:כ״ו

1ויהי כנען, his offspring [seeing that the word ויהי is in the future tense; Ed.]

2עבד למו, to the G’d as well as to the offspring of Shem. The formulation is parallel to Joshua 9,27 where the Gibeonites are condemned to be “hewers of wood and carriers of water” for the Israelites (having duped them into thinking that they were not Canaanites)