Blessed are the upright in their way, who walk in the law of the Lord. King Solomon, peace be upon him, said (Proverbs 20:7): "The righteous who walks in his integrity—blessed are his children after him!" How fortunate are his children who follow his example! The Almighty only asked of Abraham to be upright, as it says (Genesis 17:1): "Walk before Me, and be wholehearted."
Similarly, Moses said to Israel (Deuteronomy 18:13): "You shall be wholehearted with the Lord your God." The word used here is not "with" but "before." If you are wholehearted, you are with the Lord your God, just as He is wholehearted, as it says of Him (2 Samuel 22:31): "His way is perfect." Israel is wholehearted, and the Torah is wholehearted, as it says (Psalm 19:8): "The Torah of the Lord is perfect."
Therefore, it is said, "Blessed are the upright in their way," for the generation of the desert were both wholehearted and pious. Rabbi Eliezer used to say: "The Lord said to them (Exodus 22:30): 'You shall be holy men to Me; therefore you shall not eat any flesh that is torn of beasts in the field; you shall cast it to the dogs.'" He did not say why, but they accepted it upon themselves. He also said to them (Leviticus 19:23): "And when you come into the land, and have planted all manner of trees for food, then you shall count its fruit as uncircumcised; three years it shall be as uncircumcised to you; it shall not be eaten of."
He did not say why, but they accepted it upon themselves. Even though they accepted it, they did not ask, "What reward will we receive for doing them?" Therefore, it is said, "Blessed are the upright in their way," etc.