Canon 15
On establishing the canonical age for ordination to the subdeaconate – 20 years.
One cannot ordain a subdeacon before the age of 20. If anyone is ordained to any sacred degree before a certain age, let him be deposed.
Greek original
Ὑποδιάκονος μὴ ἦττον τῶν εἴκοσι ἐτῶν χειροτονείσθω· εἰ δέ τις τῶν ἐν οἱᾳοῦν ἱερατικῇ καταστάσει παρὰ τοὺς ὁρισθέντας χειροτονηθείη χρόνους, καθαιρείσθω.
Parallel canons
IVВс.15Трул.14Неокес.11Карф.16