And whence is it derived that the honor due one's friend is to be as beloved by him as the fear of his teacher? From (Numbers 12:11) "And Aaron said to Moses: 'I pray you, my lord.'" Now was Aaron not Moses' brother, and older than he? How, then, is "I pray you, my lord" to be understood? He equated him with his teacher.
When Aaron Addressed Moses After the Incident with Miriam's Leprosy
Mekhilta Tractate Amalek 1:13