מדרש אויף דברים 3:28

"Command": The command is immediately, for present performance and for future generations. You say thus, but perhaps it is only for future performance! It is, therefore, (to negate this) written "Command the children of Israel that they send … (Bamidbar 5:2) "And the children of Israel did so, sending them outside the camp" — whence we derive that the command is for immediate performance. And whence do we derive that it is (also) for future generations? From (Vayikra 24:2) "Command the children of Israel that they take to you clear olive oil … (3) … an eternal statute for your generations." — But how do we derive (the same) for all the commands in the Torah? R. Yishmael says: Since we find unqualified commands in the Torah, and one of them was qualified as being for present performance and for future generations, we derive the same for all the mitzvoth in the Torah. R. Yehudah b. Bethira says: "command" in all places connotes impulsion (to the act), as it is written (Devarim 3:28) "And command Joshua and strengthen him and fortify him" — whence we learn "We strengthen only the (internally) strengthened," and "We impel only the (internally) impelled." R. Shimon b. Yochai says: "Command" in all places entails expense, as it is written (Vayikra 24:2) "Command the children of Israel that they take to you pure olive oil," (Bamidbar 35:2) "Command the children of Israel that they give to the Levites from the inheritance, etc." (Bamidbar 28:2) "Command the children of Israel and say to them: My offering, My bread, for My fires" — whence we see that "command" in all places entails expense. Except in one; and which is that? (Bamidbar 34:2) "Command the children of Israel and say to them: When you come to the land of Canaan, etc." — where the intent is: Impel them to the division of the land. Rebbi says: "Command" in all places is exhortation, as it is written (Bereshit 2:16-17) "And the L-rd G-d commanded (i.e., exhorted) the man, saying … but of the tree of knowledge of good and evil, you shall not eat."

“Command [tzav] the children of Israel” – anywhere that command [tzav] is stated, the command is immediately at the time of the action and is practiced throughout the generations. Rabbi Yehuda ben Beteira says: Command [tzivui] is everywhere nothing other than exhortation, as it is stated: “Command Joshua and encourage him [and exhort him]” (Deuteronomy 3:28). According to our approach we learned that one encourages only the encouraged and one exhorts only the exhorted.
Rabbi Shimon ben Yoḥai says: Command, everywhere, involves monetary loss,²⁴Monetary loss means that fulfilling the commandment requires spending money. as it is stated: “Command the children of Israel and they shall take to you pure olive oil” (Leviticus 24:2); “command the children of Israel and they shall send out”; “command the children of Israel and they shall give to the Levites” (Numbers 35:2); “command the children of Israel and say to them: My offering” (Numbers 28:2). Command, everywhere, always involves monetary loss, except for one. Which is that? “Command the children of Israel and say to them that you are coming to the land, Canaan” (Numbers 34:2), which addresses the matter of the division of the land. Rabbi [Yehuda HaNasi] says: Command, everywhere, is nothing other than admonition, as it is stated: “God commanded the man…but of the tree of knowledge of good and evil [you shall not eat]” (Genesis 2:16–17).

(Devarim 3:28) "for he will pass over before this people": If he passes over before them, they will pass; if not, they will not.