The story
This simplified order first appeared in John Selden's Table-Talk (c. 1654): "Preachers say, 'Do as I say, not as I do.'" The original parsing is found in the New Testament (Matthew 23:1-3; King James Version): “Then spake Jesus to the multitude, and to his disciples, Saying The scribes and the Pharisees sit in Moses' seat: All therefore whatsoever they bid you observe, that observe and do; but do not ye after their works: for they say, and do not.”
Etymology from Wiktionary, CC BY-SA 4.0.