Adam Clarke on 2 Chronicles 15:12

They entered into a covenant - The covenant consisted of two parts:

1. We will seek the God of our fathers with all our heart, and with all our soul.

2. Whosoever, great or small, man or woman, will not worship the true God, and serve him alone, shall be put to death. Thus no toleration was given to idolatry, so that it must be rooted out: and that this covenant might be properly binding, they confirmed it with an oath; and God accepted them and their services.