Musar על אבות 4:12

בחר לנו אנשים. Rashi sees in the word לנו proof that Moses equated Joshua with himself in this task. The Rabbis deduced from this a rule that a teacher should always be as concerned with the honour of his student as with his own. The honour of someone of equal status to oneself, however, should be placed on a par with the honour of one's teacher. The source for this is found in Numbers 12,11 where Aaron, Moses' older brother, addresses him with the words: בי אדוני, "Please my lord!" The honour of one's teacher should be treated as equivalent to the honour of G–d Himself. We derive this from Numbers 11,28 where Joshua pleads with Moses to kill Eldod and Meydod for prophesying the death of Moses. The words used are: אדוני משה כלאם. Joshua felt that insubordination against his teacher Moses deserved the same penalty as insubordination against G–d Himself. We can now understand why we are taught in Avot 4,1: "Who is truly honoured? He who honours G–d's creatures."