2 Chronicles 22:10-14

Now when Athaliah the mother of Ahaziah saw that her son was dead, she rose and eliminated all the royal children of the house of Judah.

But Jehoshabeath the king’s daughter took Joash the son of Ahaziah, and stole him from among the king’s sons who were being put to death, and placed him and his nurse in the bedroom. So Jehoshabeath, the daughter of King Jehoram, the wife of Jehoiada the priest (for she was the sister of Ahaziah), hid him from Athaliah so that she would not put him to death.

He kept himself hidden with them in the house of God for six years while Athaliah reigned over the land.