If you cannot close the mouth of one who reviles his brother, at least avoid conversation with him. Isaac the Syrian
If you aren't a peacemaker at least don't be a troublemaker. Isaac the Syrian
The most important thing in life is to always do good. If you can't do great deeds for people, at least try to do something small. Luke (Voyno-Yasenetsky)
Where there is least heart there is most tongue. Italian Proverb
At the wedding-feast the least eater is the bride. Spanish Proverb
Advice when most needed is least heeded. English Proverb