Luke 2:42

42AndκαὶwhenὅτεHe wasἐγένετοyears [old]ἐτῶνtwelveδώδεκα,having gone upἀναβαινόντωνtheyαὐτῶνaccording toκατὰtheτὸcustomἔθοςof theτῆςFeastἑορτῆς

And when He was twelve years [old], [on] their having gone up according to the custom of the Feast