Judge not thy friend until ...

Judge not thy friend until thou standest in his place.
 Hillel the Elder

Quotes from the same author

Say not: When I have free time I shall study, for you may perhaps never have any free time
 Hillel the Elder
If not you, who? If not now, when?
 Hillel the Elder
Moreover he saw a skull floating on the surface of the water and he said unto it: Because you drowned others they drowned you; and those that drowned you will eventually be drowned.
 Hillel the Elder