Jeremiah 33:19-21
33:19 The Lord spoke further to Jeremiah.
33:20 “I, Lord, make the following promise: ‘I have made a covenant with the day and with the night that they will always come at their proper times. Only if you people could break that covenant
33:21 could my covenant with my servant David and my covenant with the Levites ever be broken. So David will by all means always have a descendant to occupy his throne as king and the Levites will by all means always have priests who will minister before me.