(9) Shew a miracle for you.--Pharaoh had perhaps heard of the miracles wrought by Aaron before the people of Israel (Exodus 4:30), and was curious to be an eye-witness of one, as was Herod Antipas (Luke 23:8). Or he may have thought that if Moses and Aaron "shewed a miracle," his own magicians would be able to show greater ones, and he would then dismiss the brothers as charlatans and impostors. He certainly did hot intend to be influenced by any miracle which they might show, or to accept it as evidence that their message to him was a command from God.
Verse 9. - When Pharaoh shall speak to you, saying, Shew a miracle. It is obvious that there would have been an impropriety in Moses and Aaron offering a sign to Pharaoh until he asked for one. They claimed to be ambassadors of Jehovah, and to speak in his name (Exodus 5:1). Unless they were misdoubted, it was not for them to produce their credentials. Hence they worked no miracle at their former interview. Now, however, the time was come when their credentials would be demanded, and an express command was given them to exhibit the first "sign."
7:8-13 What men dislike, because it opposes their pride and lusts, they will not be convinced of; but it is easy to cause them to believe things they wish to be true. God always sends with his word full proofs of its Divine authority; but when men are bent to disobey, and willing to object, he often permits a snare to be laid wherein they are entangled. The magicians were cheats, trying to copy the real miracles of Moses by secret sleights or jugglings, which to a small extent they succeeded in doing, so as to deceive the bystanders, but they were at length obliged to confess they could not any longer imitate the effects of Divine power. None assist more in the destruction of sinners, than such as resist the truth by amusing men with a counterfeit resemblance of it. Satan is most to be dreaded when transformed into an angel of light.
When Pharaoh shall speak unto you, saying, show a miracle for you,.... To prove that they came from God, the Jehovah they said they did, and that they were his ambassadors, and came in his name, and made the demand for him; which when he seriously reflected on things, he would be ready to require, hoping they would not be able to show any, and then he should have somewhat against them, and treat them as impostors:
then thou shalt say unto Aaron, take thy rod; the same that Moses had in his hand at Horeb, and brought with him to Egypt; this he had delivered into the hand of Aaron, who was to be his agent, and with this rod do signs and wonders as he did, and on account of them it is sometimes called the rod of God:
and cast it before Pharaoh, and it shall become a serpent; as it became one before at Horeb, when Moses by the order of God cast it on the ground, and afterwards became a rod again, as it now was, Exodus 4:2 Hence Mercury, the messenger of the gods with the Heathens, is represented as having a "caduceus", a rod or wand twisted about with snakes (p).
(p) Vid. Chartar. de Imag. Deorum, p. 136. imag. 48.
Thy rod.--The rod is now called Aaron's, because Moses had entrusted him with it. (Comp. Exodus 7:19, and Exodus 8:5; Exodus 8:16-17.)
A serpent.--Or, a snake. The word is not the same as that used in Exodus 4:3, but appears to be a synonym.
CHAPTER 7:10-13
then thou shalt say unto Aaron, take thy rod; the same that Moses had in his hand at Horeb, and brought with him to Egypt; this he had delivered into the hand of Aaron, who was to be his agent, and with this rod do signs and wonders as he did, and on account of them it is sometimes called the rod of God:
and cast it before Pharaoh, and it shall become a serpent; as it became one before at Horeb, when Moses by the order of God cast it on the ground, and afterwards became a rod again, as it now was, Exodus 4:2 Hence Mercury, the messenger of the gods with the Heathens, is represented as having a "caduceus", a rod or wand twisted about with snakes (p).
(p) Vid. Chartar. de Imag. Deorum, p. 136. imag. 48.