One Who Makes Himself Like a Pauper Will Daven Properly
The Divrei Shmuel of Slonim zy”a notes that the word “tetzaveh” can be an acronym for “tze’akas hadal takshiv v’soshiah.” Hear the cry of the pauper and save him. This indicates that a haughty man cannot properly daven to Hashem. Only a person who holds himself lowly can speak to Him.
Chazal say (Kesuvos 77B, Avos D’rov Nosson 9:2): “There are 24 types of people who are diseased with boils, and the soul of Moshe was lowlier than all of them.” He was very lowly in his own eyes, but he still poured his heart out in prayer before Hashem and told Him that if He wiped out Klal Yisroel, He should erase his name from the Torah (Shemos 32:32). In this case he prayed for the public as a whole, and he also prayed for Miriam in particular, when he asked Hashem to heal her (Bamidbor 12:13).
When Hashem told Moshe: “Ata Tetzaveh” (you shall command), He was telling him to pass on the message of hearing the cries of the pauper. He was told to teach us that even if think of ourselves as insignificant, we should still daven to Hashem, and He will hear our prayers.