A.T. Robertson Commentary Matthew 20:26

"Not so shall it be among you: but whosoever would become great among you shall be your minister;" — Matthew 20:26 (ASV)

Would become great (ος αν θελη μεγας γενεσθα). Jesus does not condemn the desire to become great. It is a laudable ambition. There are "great ones" (μεγαλο) among Christians as among pagans, but they do not "lord it over" one another (κατακυριευουσιν), a LXX word and very expressive, or "play the tyrant" (κατεξουσιαζουσιν), another suggestive word.

Your minister (υμων διακονος). This word may come from δια and κονις (dust), to raise a dust by one's hurry, and so to minister. It is a general word for servant and is used in a variety of ways including the technical sense of our "deacon" in Php. 1:1. But it more frequently is applied to ministers of the Gospel (1 Corinthians 3:5). The way to be "first" (πρωτος), says Jesus, is to be your "servant" (δουλος), "bond-servant" (verse 27). This is a complete reversal of popular opinion then and now.