Deuteronomy Chapter 29, Verse 9

9: Keep therefore the words of this covenant, and do them, that ye may prosper in all that ye do.- edit KJV text
9: Keep therefore the words of this covenant, and fulfil them: that you may understand all that you do.— edit Douay text
9: And ye shall take heed to do all the words of this covenant, that ye may understand all things that ye shall do.— edit LXX text