Samyutta Nikaya I. 222
You make things worse when you flare up at someone who's angry. Whoever doesn't flare up at someone who's angry wins a battle hard to win. You live for the good of both—your own, the other's—when, knowing the other's provoked, you mindfully grow calm. When you work the cure of both—your own, the other's—those who think you a fool know nothing of Dhamma.