John Calvin Commentary Genesis 9:26

"And he said, Blessed be Jehovah, the God of Shem; And let Canaan be his servant." — Genesis 9:26 (ASV)

Blessed be the Lord God of Shem. Noah blesses his other children, but in a different manner, for he places Shem in the highest post of honor. And this is the reason why Noah, in blessing him, breaks out in the praise of God, without limiting his praise to the man himself.

For the Hebrews, when they speak of any rare and transcendent excellence, raise their thoughts to God. Therefore, the holy man, when he perceived that the most abundant grace of God was destined for his son Shem, rises to thanksgiving.

From this we infer that he spoke, not from carnal reason, but rather spoke of the hidden blessings of God, whose fulfillment would be delayed until a distant time. Finally, by these words it is declared that the blessing of Shem would be divine or heavenly.