Deuteronomy 8:19 in the King James Version
And it shall be, if thou do at all forget the LORD thy God, and walk after other gods, and serve them, and worship them, I testify against you this day that ye shall surely perish.
Context
18 But you shall remember the LORD your God, for it is he who gives you power to get wealth, that he may establish his covenant which he swore to your fathers, as it is today.
19 It shall be, if you shall forget the LORD your God, and walk after other gods, and serve them and worship them, I testify against you today that you shall surely perish.
20 As the nations that the LORD makes to perish before you, so you shall perish, because you wouldn’t listen to the LORD your God’s voice.