Leviticus Rabbah 34:10

R. Abbahu in the name of R. Eliezer said: We ought to be grateful to the imposters, since were it not for the imposters among the poor, then if any of them begged from a person who refused, the latter would immediately incur the penalty of death; for it says, “And the poor cry unto the Lord against you, and it be sin,” and it furthers says, “The person who sins, only they shall die.” (Ezekiel 18:4). R. Yohanan and Resh Lakish went down to bathe in the public baths at Tiberias. A poor man met them and said to them: “Give me alms.” They replied: “When we come out we shall acquire merit through you.” When they came out they found that he was dead. They remarked: “Seeing that we did not attend to him in his lifetime, let us attend to him at his death.” As they were washing him they found a bag containing six hundred denarii suspended from his neck. They exclaimed: “Blessed be God who has chosen the wise and their words! Did not R. Abbahu actually state in the name of R. Eliezer: We ought to be grateful to imposters, etc?” [Soncino translation. Edited for gender neutrality]