Midrash su Salmi 50:16

Our Rabbis were taught: It happened that Acher was riding upon his horse on the Sabbath, and R. Mair was walking behind him to learn the Torah from his mouth. He said to him: "Mair, turn thee backwards, for I have already measured by means of my horse's hoofs that up to this point is the legal limit of the Sabbath." R. Mair then said to him: "Return thyself also." Whereupon Acher replied. "Have I not answered thee already what I have heard from behind the curtain?" R. Mair forced him to enter a place of learning. He said to a child: "Repeat for me thy verse," [which thou hadst studied today.] He quoted to him: (Is. 48, 22) There is no peace, saith the Lord, unto the wicked. He brought him to another house of learning. Acher said to a child: "Repeat for me thy verse." The child quoted to him: (Jer. 2, 22) For though thou wash thee with nitre, and take thee much soap, yet thine iniquity is marked before Me. He then brought him to another place of learning, whereupon Acher said to a child: "Repeat for me thy verse." The child quoted: (Ib. 4, 30) And thou, (Ib. b) that are spoiled, what dost thou, that thou clothest thyself with scarlet, that thou deckest thee with ornaments of gold, that thou enlargest thine eyes with paint? In vain dost thou make thyself fair. He forced Acher to enter thirteen houses of learning and all quoted to him the same way. In the last one he said to the child: "Repeat for me thy verse." The child quoted to him (Ps. 50. 16) But unto the wicked (V'larasha) God saith: What hast thou to do to declare My statutes. That child was a stammerer and it sounded as if he had said Vle'elish [instead of V'larasha]. God saith, etc., whereupon Acher drew out a knife and cut the child into pieces and sent it to the thirteen houses of learning. According to others he only remarked: "If there had been a knife in my possession I would have cut him in pieces."

An idolater asked Rabban Gamliel, "Why was the Holy One, Blessed be He revealed to Moses in the Burning Bush?" Rabban Gamliel replied to him, "If God had been revealed in a carob tree or a fig tree, you would have asked me the same thing, and I could not send you away without an answer. This teaches you that there is no place in the world devoid of the Shekhinah."