A rabbi is talking with his students and asks them, "How do you know that the dawn has arrived so that you can say your morning prayers?"

They propose various answers: "When it is light enough to tell the difference between a goat and a donkey." "When it is light enough to distinguish between a fig tree and an olive tree."

The rabbi answers, "No, it is when you can look into the face of a stranger and see your brother or sister. Then you know that the darkness of night has ended and the light of dawn has arrived."