and when they had fulfilled the days, as they were returning, the boy Jesus tarried behind in Jerusalem; and his parents knew it not;

And when the days of the feast came to an end and they were going back, the boy Jesus was still in Jerusalem, but they had no knowledge of it:

και ετελειωσαν τας ημερας, ενω αυτοι υπεστρεφον, το παιδιον ο Ιησους εμεινεν οπισω εν Ιερουσαλημ, και δεν ενοησεν ο Ιωσηφ και η μητηρ αυτου.

And when they had fulfilled the days, as they returned, the child Jesus tarried behind in Jerusalem; and Joseph and his mother knew not of it.