Musar על נדרים 100:16

He should also rejoice when he sees the rejoicing of the wicked and the pleasures of transgressors and he should think thusly "If those who transgress God's Will can rejoice thus, then how much more will those who do His Will rejoice" (Nedarim 50b). And concerning this David says, "You have placed a joy in my heart greater than their joy in their plentiful corn and wine" (Ps. 4:8). For example, a king invited guests and when they reached the courtyard of the king they saw the dogs eating ducks and chickens and they said : "If dogs are treated thus, then how much better will be our portion" (Shohar Tob, Midrash on Ps. 4:11).