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. Had fulfilled the days - Eight days in the whole: one was the passover, and the other seven, the days of unleavened bread. See on Matthew 26:2 (note).
Related Commentaries of Luke 2:43
Luke 2:43
43 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.