GEN593 The Holy One Blessed be He exiled the Jews among the nations only so that converts should be added to their numbers Pesachim 87b.  If the Jews deal with them without deceit, they will cleave to them. And the Holy One Blessed be He looked with disfavor upon the stealing of the wicked (this verse).  It is told Deuteronomy Rabbah 3:3 that the disciples of Rabbi Shimon ben Shatach, finding a precious stone hanging from the neck of a donkey that he had purchased from an Ishmaelite, brought it to him and said: “Our master, ‘The blessing of Hashem makes one rich’ Proverbs 10:22.  [i.e., This is a gift to you from God], to which he replied, “I bought a donkey; I did not buy a precious stone.”  Thus saying, he went and returned the stone to the Ishmaelite, who thereupon proclaimed: “Blessed is Hashem, the God of Shimon ben Shatach.”  TZADIK 403-305