R. Nathan says: This is the retort to those heretics who would contend that there are two Deities. When the Holy One Blessed be He stood (at Mount Sinai) and said "I am the L–rd your G–d," who stood up and contended with Him? If you would say that this took place in concealment, is it not written (Ibid. 45:19) "Not in secret did I speak, etc." I did not reserve it (the Torah) for them alone. And thus is it written (Ibid.) "I, the L–rd, speak righteously; I tell what is true."