John Calvin on Luke 16:21

21. And even the dogs came. It was quite enough to prove the hardened cruelty of the rich man, that the sight of wretchedness like this did not move him to compassion. Had there been a drop of humanity in him, he ought at least to have ordered a supply from his kitchen for the unhappy man. But the crowning exhibition of his wicked, and savage, and worse than brutal disposition was, that he did not learn pity even from the dogs There can be no doubt that those dogs were guided by the secret purpose of God, to condemn that man by their example. Christ certainly produces them here as witnesses to convict him of unfeeling and detestable cruelty. What could be more monstrous than to see the dogs taking charge of a man, to whom his neighbor is paying no attention; and, what is more, to see the very crumbs of bread refused to a man perishing of hunger, while the dogs are giving him the service of their tongues for the purpose of healing his sores? When strangers, or even brute animals, supply our place, by performing an office which ought rather to have been discharged by ourselves, let us conclude that they are so many witnesses and judges appointed by God, to make our criminality the more manifest.