Original Verse:
Luke Chapter 2 Verse 43And 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:

Reference Verses:
Exodus Chapter 12 Verse 15For seven days let your food be unleavened bread; from the first day no leaven is to be seen in your houses: whoever takes bread with leaven in it, from the first till the seventh day, will be cut off from Israel.
2nd Chronicles Chapter 30 Verse 21-23 [21] So the children of Israel who were present in Jerusalem kept the feast of unleavened bread for seven days with great joy: and the Levites and the priests gave praise to the Lord day by day, making melody to the Lord with loud instruments. [22] And Hezekiah said kind words to the Levites who were expert in the ordering of the worship of the Lord: so they kept the feast for seven days, offering peace-offerings and praising the Lord, the God of their fathers. [23] And by the desire of all the people, the feast went on for another seven days, and they kept the seven days with joy.
2nd Chronicles Chapter 25 Verse 17Then Amaziah, king of Judah, acting on the suggestion of his servants, sent to Joash, the son of Jehoahaz, the son of Jehu, king of Israel, saying, Come, let us have a meeting face to face.