And the Lord spake. No wonder that Moses often repeats the same thing, because he wrote for persons of rude and dull minds. But it behooves us, lest we should be disgusted by his simple and popular style, diligently to examine how little we are inclined to be acute and earnest in our consideration of the works of God. No doubt there is here related what we have already heard respecting the change of the rod into a serpent, except that he now tells us that the miracle which had before been performed in the wilderness of Midian, and afterwards in Egypt, in the sight of the people, was likewise performed once more before Pharaoh. Moreover, we gather from hence that at the request of Pharaoh the servants of God had proved and testified their vocation; and therefore that his pertinacity was the less excusable, since he despised the power of God so manifestly shewn forth. For this is usual with unbelievers, to demand proofs of God's power, which they may still discredit, -- not that they professedly scorn God, but because their secret impiety urges them to seek after subterfuges. The message is disagreeable and full of what is annoying to the proud king; and because he does not dare directly to refuse God, he invents a plausible pretext for his refusal, by asking for a miracle; and when this is performed, he seeks still deeper lurking places, as we shall very soon perceive. Since, therefore, it was certain that he would not pay a willing obedience to the divine command, and would not yield before he had been miraculously convinced, God furnishes His servants with a notable and sure testimony of His power. Moreover, the change of the crook, or shepherd's staff, into a serpent had this object, namely, that the mean and rustic guise of Moses should not be despised. For (since kings are wont to exalt themselves very highly) Pharaoh might have laughed at the audacity of Moses and Aaron, who, forgetful, as it seemed, of their condition, put themselves into conflict with the whole power of Egypt; but Pharaoh knew, although they were not to be dreaded for their splendid appearance, and had nothing magnificent about them, that they were still not destitute of sure and strong help, when he saw the serpent come forth from the rod. In a word, God bore witness that His power is hidden beneath the infirmity of His servants, so that at every season He might render formidable to the greatest monarchs those who otherwise are like earthen vessels. It is not clear to me why Aaron was commanded to cast down the rod rather than Moses, unless, perhaps, because God would designedly humble the pride of the arrogant king, when He did not deign to exert His power by the hand of His superior servant, but only employed the inferior one. Therefore, with reference to this ministration, the rod of God and of Moses is now called the rod of Aaron. Thus Paul boasts of his gospel, the office of preaching which he knew to be committed to him. (Romans 16:25, and 2-Timothy 2:8.)

And the Lord spake unto Moses and unto Aaron,.... After he had given them their commission, and instructions to go to Pharaoh, and a little before they went in to him:
saying, as follows.

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.

The negotiations of Moses and Aaron as messengers of Jehovah with the king of Egypt, concerning the departure of Israel from his land, commenced with a sign, by which the messengers of God attested their divine mission in the presence of Pharaoh (Exodus 7:8-13), and concluded with the announcement of the last blow that God would inflict upon the hardened king (Exodus 11:1-10). The centre of these negotiations, or rather the main point of this lengthened section, which is closely connected throughout, and formally rounded off by Exodus 11:9-10 into an inward unity, is found in the nine plagues which the messengers of Jehovah brought upon Pharaoh and his kingdom at the command of Jehovah, to bend the defiant spirit of the king, and induce him to let Israel go out of the land and serve their God. If we carefully examine the account of these nine penal miracles, we shall find that they are arranged in three groups of three plagues each. For the first and second, the fourth and fifth, and the seventh and eighth were announced beforehand by Moses to the king (Exodus 7:15; Exodus 8:1, Exodus 8:20; Exodus 9:1, Exodus 9:13; Exodus 10:1), whilst the third, sixth, and ninth were sent without any such announcement (Exodus 8:16; Exodus 9:8; Exodus 10:21). Again, the first, fourth, and seventh were announced to Pharaoh in the morning, and the first and fourth by the side of the Nile (Exodus 7:15; Exodus 8:20), both of them being connected with the overflowing of the river; whilst the place of announcement is not mentioned in the case of the seventh (the hail, Exodus 9:13), because hail, as coming from heaven, was not connected with any particular locality. This grouping is not a merely external arrangement, adopted by the writer for the sake of greater distinctness, but is founded in the facts themselves, and the effect which God intended the plagues to produce, as we may gather from these circumstances - that the Egyptian magicians, who had imitated the first plagues, were put to shame with their arts by the third, and were compelled to see in it the finger of God (Exodus 8:19), - that they were smitten themselves by the sixth, and were unable to stand before Moses (Exodus 9:11), - and that after the ninth, Pharaoh broke off all further negotiation with Moses and Aaron (Exodus 10:28-29). The last plague, commonly known as the tenth, which Moses also announced to the king before his departure (Exodus 11:4.), differed from the nine former ones both in purpose and form. It was the first beginning of the judgment that was coming upon the hardened king, and was inflicted directly by God Himself, for Jehovah "went out through the midst of Egypt, and smote the first-born of the Egyptians both of man and beast" (Exodus 11:4; Exodus 12:29); whereas seven of the previous plagues were brought by Moses and Aaron, and of the two that are not expressly said to have been brought by them, one, that of the dog-flies, was simply sent by Jehovah (Exodus 8:21, Exodus 8:24), and the other, the murrain of beasts, simply came from His hand (Exodus 9:3, Exodus 9:6). The last blow (נגע Exodus 11:1), which brought about the release of Israel, was also distinguished from the nine plagues, as the direct judgment of God, by the fact that it was not effected through the medium of any natural occurrence, as was the case with all the others, which were based upon the natural phenomena of Egypt, and became signs and wonders through their vast excess above the natural measure of such natural occurrences and their supernatural accumulation, blow after blow following one another in less than a year, and also through the peculiar circumstances under which they were brought about. In this respect also the triple division is unmistakeable. The first three plagues covered the whole land, and fell upon the Israelites as well as the Egyptians; with the fourth the separation commenced between Egyptians and Israelites, so that only the Egyptians suffered from the last six, the Israelites in Goshen being entirely exempted. The last three, again, were distinguished from the others by the fact, that they were far more dreadful than any of the previous ones, and bore visible marks of being the forerunners of the judgment which would inevitably fall upon Pharaoh, if he continued his opposition to the will of the Almighty God.
In this graduated series of plagues, the judgment of hardening was inflicted upon Pharaoh in the manner explained above. In the first three plagues God showed him, that He, the God of Israel, was Jehovah (Exodus 7:17), i.e., that He ruled as Lord and King over the occurrences and powers of nature, which the Egyptians for the most part honoured as divine; and before His power the magicians of Egypt with their secret arts were put to shame. These three wonders made no impression upon the king. The plague of frogs, indeed, became so troublesome to him, that he begged Moses and Aaron to intercede with their God to deliver him from them, and promised to let the people go (Exodus 8:8). But as soon as they were taken away, he hardened his heart, and would not listen to the messengers of God. Of the three following plagues, the first (i.e., the fourth in the entire series), viz., the plague of swarming creatures or dog-flies, with which the distinction between the Egyptians and Israelites commenced, proving to Pharaoh that the God of Israel was Jehovah in the midst of the land (Exodus 8:22), made such an impression upon the hardened king, that he promised to allow the Israelites to sacrifice to their God, first of all in the land, and when Moses refused this condition, even outside the land, if they would not go far away, and Moses and Aaron would pray to God for him, that this plague might be taken away by God from him and from his people (Exodus 8:25.). But this concession was only forced out of him by suffering; so that as soon as the plague ceased he withdrew it again, and his hard heart was not changed by the two following plagues. Hence still heavier plagues were sent, and he had to learn from the last three that there was no god in the whole earth like Jehovah, the God of the Hebrews (Hebrews 9:14). The terrible character of these last plagues so affected the proud heart of Pharaoh, that twice he acknowledged he had sinned (Exodus 9:27; Exodus 10:16), and gave a promise that he would let the Israelites go, restricting his promise first of all to the men, and then including their families also (Exodus 10:11, Exodus 10:24). But when this plague was withdrawn, he resumed his old sinful defiance once more (Exodus 9:34-35; Exodus 10:20), and finally was altogether hardened, and so enraged at Moses persisting in his demand that they should take their flocks as well, that he drove away the messengers of Jehovah and broke off all further negotiations, with the threat that he would kill them if ever they came into his presence again (Exodus 10:28-29).