Avoir le cœur sur la main

Literally: To have your heart on your hand

Example: “Mon grand-père a le cœur sur la main, il aide tout le monde.” — My grandfather has a heart of gold; he helps everyone.

English equivalent: To have a heart of gold

Origin: The heart, seat of the feelings, held out in an open hand: nothing is hidden and everything is offered. The phrase dates from the 18th century, and its first meaning was frankness: the grammarian Féraud defined it in 1787 as being frank and not secretive. The sense of generosity, now the usual one, grew from the same gesture of the open hand.