What does "do as I say" mean?

Obey my instructions, as in Never mind about the other mothers—you do as I say. This admonitory order is sometimes followed by a self-deprecating phrase, Do as I say, not as I do, meaning “don't imitate my behavior but obey my instructions.” This order first appeared in John Selden's Table-Talk (c. 1654): “Preachers say, 'Do as I say, not as I do.'”