If you ever forget the LORD your God and go after other gods to worship and bow down to them, I testify against you today that you will surely perish.
KJV
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.
ASV
And it shall be, if thou shalt forget Jehovah thy God, and walk after other gods, and serve them, and worship them, I testify against you this day that ye shall surely perish.