What did HaSh-m mean when He said to Yitzchak that, "All the nations of the land will be blessed in your offspring"?
Targum Onkelos and Targum Yonasan: All the nations of the land will be blessed because of you!' (I.e. that Yisrael will be the conduit through which Berachah will flow on to the whole world). 3
QUESTIONS ON RASHI
Rashi writes: "'They shall bless themselves (v'Hisbarechu)' - A person would say to his son, 'may your children be like Yitzchak's.'" Why doesn't Rashi explain that all the nations would receive a blessing in Yitzchak's merit?
Gur Aryeh: The word "v'Hisbarechu" is in the reflexive, indicating something one does to oneself. Rashi therefore explains that a person would bless his own family.