Дварим 4:37 Комментарий: Rashi, Chizkuni, Ibn Ezra & Sforno

ותחת כי אהב AND BECAUSE HE LOVED — i.e., and all this was because He loved thy fathers.

ויבחר בזרעו אחריו, “and chose their seed after them;” this is a hint to Yaakov; if the Torah had written: בזרעם אחריהם, it could have been interpreted as eight nations. (the six sons of Keturah, Esau and Ishmael) all of whom had emerged from Avraham and Yitzchok) in addition to the Jewish people.

his descendants an allusion to Yaaqov. To say “their descendants” would include eight other nations with us!

ויוצאך בפניו AND HE BROUGHT THEE OUT BEFORE HIM — like a man who leads his son before him, as it is said, (Exodus 14:19) “And the angel of the Lord that went [before them] moved and went behind them" (see Rashi on that verse). — Another explanation of ויוצאך בפניו AND HE BROUGHT THEE FORTH IN HIS PRESENCE: — i.e. in the presence of his fathers, as it is said, (Psalms 78:12; see Rashi on that verse), “In the presence of their fathers He did wonders". Do not be surprised that it refers to them (the fathers) in the singular number (by בפניו), for you see it has already written about them in the singular number, viz., “And he chose his seed after him" (instead of “their seed after them").