What Is the Lord's Sworn Covenant?

Beware, lest there be among you a root bearing poisonous and bitter fruit. One who when he hears the words of this sworn covenant blesses himself in his heart saying "I shall be safe" This would lead to the sweeping away of moist and dry alike. The Lord would not pardon him, but rather the anger of the Lord and his jealousy would smoke against that man. And the curses written in this book would settle upon him, and the Lord would blot out his name from under heaven.