Luke 2:43 in the King James Version
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.
Context
42 When he was twelve years old, they went up to Jerusalem according to the custom of the feast;
43 and when they had fulfilled the days, as they were returning, the boy Jesus stayed behind in Jerusalem. Joseph and his mother didn’t know it,
44 but supposing him to be in the company, they went a day’s journey; and they looked for him among their relatives and acquaintances.