Altho’ thy Teacher act not as he preaches,
Yet ne’ertheless, if good, do what he teaches;
Good Counsel, failing Men may give; for why,
He that’s aground knows where the Shoal doth lie.
My old Friend Berryman, oft, when alive,
Taught others Thrift; himself could never thrive:
Thus like the Whetstone, many Men are wont
To sharpen others while themselves are blunt.

Benjamin Franklin (1706-1790) American statesman, scientist, philosopher, aphorist

Poor Richard (1734 ed.)
    (Source)