פּירוש אויף דברים 29:8

ושמרתם את דברי הברית הזאת, “observe therefore the words of this covenant;” you are obligated to do so in light of all the favours the Lord has done for you as recorded earlier.

The verb achieve is in the hif’il form, like the word “succeed” [Jeremiah 32: 5]. It is a transitive verb with both a direct and an indirect object, as evidenced by the word you do. Compare, “David achieved in all his endeavors” [I Samuel 18: 14].

“And you shall observe, etc., and perform them, so that you may prosper in all that you do.” Since one mitzvah leads to another mitzvah (Avot 4:2), therefore he says that one mitzvah causes you to prosper in all that you do, because each one leads to its companion. And this is what is meant (ibid.) when it says that the reward of a mitzvah is [another] mitzvah. And this is what is meant by you shall observe and perform them, because the observance will lead to the performance, and the reward for the performance is so that you may prosper further in the future in all that you do.