Do not let grass grow on the path of friendship.
More French Proverbs:
Who cannot work out his salvation by heart will not do it by book.French
One blind man leads another into the ditch.
French
Money makes dogs dance.
French
He beat the bushes and another caught the birds.
French
Whosoever draws his sword against the prince must throw the scabbard away.
French
A man at five may be a fool at fifteen.
French