"The grace of a drop of water is rewarded by a spring", which is human nature and advocates the righteous act of being brave and helping others. Despise profit and forget righteousness, ingratitude. When two good friends were traveling together, one accidentally cut the other's hand and quickly said sorry. The injured man smiled and said nothing, so he wrote on the desert with his finger: "My good friend cut off my hand today." Once again, when he accidentally sprained his ankle, his friends took good care of him until his foot recovered slowly. He carved on the stone with a knife: "My friend helped me today." When his friend asked him why in confusion, he said, "It was written in the desert to make the wind help me forget yesterday's unhappiness, and it was carved on a stone to make the years help me remember your help." My friends, who can treat others with a grateful heart like them?