We would rather speak ill of ourselves than not talk about ourselves at all. François de La Rochefoucauld
We should keep silent about those in power; to speak well of them almost implies flattery; to speak ill of them while they are alive is dangerous, and when they are dead is cowardly. Jean de La Bruyère
Let no one be willing to speak ill of the absent. Propertius
Lay your hand on your bosom and you will not speak ill of another. Portuguese Proverb
Better be silent than speak ill. Portuguese Proverb
Who speaks ill of others to you will speak ill of you to others. German Proverb