Why does it say "Gibor ba'Aretz Yihyeh Zar'o"?
Radak: Due to his good deeds, Hashem will pay also his seed after him. People will fear and honor his seed, like they fear a Gibor.
Radak citing Eduyos 2:9: His children will be strong. This is among a person's Brachos in this world. A person merits for his sons for strength, wealth, beauty, Chachmah and years (long life).
Radak, based on Shocher Tov: Verse 1 refers to Avraham (refer to 112:1:5:3), and this verse refers to Yakov - "va'Yashar El Mal'ach va'Yuchal" (Hoshe'a 12:5).
Malbim: The one who fears Hashem is happy in this world and the world to come, and also his seed. In this world, they will be Giborim. In the world to come he will be blessed, for a generation of straight people will come from him.
What is the "Dor Yesharim"?
Radak #1: The father and son are straight.
Radak #2: These are the Shevatim.
What is the meaning of "Dor Yesharim Yevurach"?
Rashi: His seed will be a straight generation that is blessed.
Radak citing his father: Hashem blessed David and Shlomo with added good.
