Then they said to Jeremiah, “May the LORD be a true and faithful witness against us if we do not act upon every word that the LORD your God sends you to tell us.
KJV
Then they said to Jeremiah, The LORD be a true and faithful witness between us, if we do not even according to all things for the which the LORD thy God shall send thee to us.
ASV
Then they said to Jeremiah, Jehovah be a true and faithful witness amongst us, if we do not according to all the word wherewith Jehovah thy God shall send thee to us.