Μὴ πολλοὶ διδάσκαλοι γίνεσθε, ἀδελφοί μου, εἰδότες ὅτι μεῖζον κρίμα λημψόμεθα.
Do not (or let not) many (of you) become teachers, my brethren, knowing that stricter judgment we will receive.
As a Christian reading the Scriptures, I have understood this verse and passage to be a warning, but have not taken it any further than just that. I had never considered the question of whether or not this negative imperative is a suggestion or command though. That is, not until reading it in my GNT. In English I usually read the ESV which states, "not many of you should become teachers...". In contemporary English this could be understood as a mere suggestion, at least that's how I understood it. The NAS says it this way, "Let not many of you become teachers..." which carries more of a command.