Gold is tested by fire, man by gold

Similar sayings:

When you want to test the depths of a stream, don’t use both feet When you want to test the depths of a stream, don’t use both feet
Long roads test the horse, long dealings the friend Long roads test the horse, long dealings the friend
Fight fire with fire Fight fire with fire
A book holds a house of gold A book holds a house of gold
Rare commodities are worth more than gold Rare commodities are worth more than gold

Chinese sayings and proverbs