Musar zu Schemot 5:2

Thus it happened to Pharaoh, who said (Ex. v. 2), "Who is the Lord?" and Goliath when he spake (I Sam. xvii. 10), "I defy the armies of Israel ; " and Sennacherib for his boastfulness in saying (II Kings xviii. 35), "Who are they among all the gods of the countries "; and Nebuchadnezzar in that he said (Dan. iii. 15), "Who is that God that shall deliver you out of my hands?" and others who follow them in the manner of their speech and whose end was complete abasement and utter obscurity. Whosoever is in this state is not secure from error and sin. Thus saith the sage (Prov. xxi. 24), "Proud and haughty scorner is his name." He mentions craftiness, because it is the source of boastfulness.

Whoever has the quality of arrogance ought to try and turn away from it for it is very base, and the damage caused by it is great and ever-present, and the worth that is in it is very little. Therefore, we must distance ourselves from it with all our might, for arrogance brings man to ruin and to humiliation, as it is said: "Pride goes before destruction" (Prov. 16:18), and it is also said: "A man's pride shall bring him low" (Prov. 29:23). And you already know what happened to Pharaoh when he said, "Who is the Lord, that I should hearken unto His voice to let Israel go?" (Exod. 5:2), and to Goliath, the Phillistine, who said: "I do taunt the armies of Israel this day" (I Sam. 17:10), and to Sennacherib, who said, "Who are they among all the gods of these countries that have delivered their country out of my hand ?" (Is. 36:20). And Nebeuchadnezzar, when he said, "And who is the god that shall deliver you from my hand?" (Dan. 3:15), and similar instances of those who spoke thusly, and their end was shame and disgrace. And whoever clings to this quality is not saved from sin and wrongdoing, as the Sage said, "A proud and haughty man, scorner is his name. Even he that dealeth in overbearing pride" (Prov. 21:24).

Whenever Moses appeared before Pharaoh he appeared as a messenger of that attribute. Pharaoh's reaction in Exodus 5,2 was that he had certainly never heard of such an attribute of any deity, מי י-ה-ו-ה אשר אשמע בקלו? Pharaoh had no difficulty in accepting G–d in His attribute as אלקים, as we know from Genesis 41,38. The Zohar (Sullam edition Miketz page 13) already comments on Genesis 41,16 where Joseph says: אלקים יענה את שלום פרעה "G–d will provide a reply for the welfare of Pharoh." Rabbi Abba said: "Observe the wickedness of Pharaoh who claimed not to have heard of G–d. He was extremely clever and exploited the fact that Moses had not presented himself as a messenger of אלקים -whom he could not have denied- but as a messenger of י-ה-ו-ה. He found it puzzling that Moses did not come in the name of the "same" G–d as the G–d of Joseph whom he recognised. He could not come to terms with that name of G–d. When the Torah writes ויחזק י-ה-ו-ה את לב פרעה, the meaning is that it was the use of that name that made Pharaoh's heart become obstinate. This is the reason that Moses never used a different name for G–d when confronting Pharaoh. Thus far the Zohar.