Is the extra compensation beyond the effort expended in work lawful?

It is permissible for the hirer to give the hired person extra wages beyond their effort as a donation, and there is no harm in giving or taking it. This is considered an act of generosity and good conduct. Its permissibility is supported by the story of the man who hired a worker for half the wages of his companions, then gave him the same as them when he saw his effort, saying: "It is my money; I may dispose of it as I wish."