Midrasch zu Wajikra 8:36

38) (Vayikra 8:35): "And at the door of the tent of meeting shall you sit day and night seven days. And you shall keep the charge of the L–rd seven days.": Now does this not follow a fortiori: If the L–rd receives (with favor) one who fulfills the words of flesh and blood (i.e., Moses, who is only His emissary), how much more so does He (thus) receive one who fulfills the words of the L–rd Himself (i.e., the words uttered at Mount Sinai)! (Vayikra 8:36): "And Aaron and his sons did" with joy and gladness in fulfilling what they had heard from the mouth of Moses just as if they had heard it from the mouth of the Holy One Blessed be He Himself! — wherefore it is written: "And Aaron and his sons did all the things that the L–rd had commanded." "by the hand of Moses": Worthy is the messenger, of his Sender! Worthy is the commanded (Aaron and his sons) of the command!