Canon 11
About ordination to the presbyter no earlier than 30 years of age.
One cannot ordain a presbyter before the age of 30, but one must wait, even if the person is very worthy, for the Lord Jesus Christ was baptized and began to teach in the 30th year.
Greek original
Πρεσβύτερος πρὸ τῶν τριάκοντα ἐτῶν μὴ χειροτονείσθω, ἐὰν καὶ πάνυ ᾖ ὁ ἄνθρωπος ἄξιος, ἀλλὰ ἀποτηρείσθω. Ὁ γὰρ Κύριος Ἰησοῦς Χριστὸς ἐν τῷ τριακοστῷ ἔτει ἐβαπτίσθη, καὶ ἤρξατο διδάσκειν.
Parallel canons
Трул.14