A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
exo 5:1FIRST INTERVIEW WITH PHARAOH. (Exo. 5:1-23)
Moses and Aaron went in--As representatives of the Hebrews, they were entitled to ask an audience of the king, and their thorough Egyptian training taught them how and when to seek it.
and told Pharaoh--When introduced, they delivered a message in the name of the God of Israel. This is the first time He is mentioned by that national appellation in Scripture. It seems to have been used by divine direction (Exo 4:2) and designed to put honor on the Hebrews in their depressed condition (Heb 11:16).
exo 5:2And Pharaoh said, Who is the Lord--rather "Jehovah." Lord was a common name applied to objects of worship; but Jehovah was a name he had never heard of. Pharaoh estimated the character and power of this God by the abject and miserable condition of the worshippers and concluded that He held as low a rank among the gods as His people did in the nation. To demonstrate the supremacy of the true God over all the gods of Egypt, was the design of the plagues.
I know not the Lord, neither will I let Israel go--As his honor and interest were both involved he determined to crush this attempt, and in a tone of insolence, or perhaps profanity, rejected the request for the release of the Hebrew slaves.
exo 5:3The God of the Hebrews hath met with us--Instead of being provoked into reproaches or threats, they mildly assured him that it was not a proposal originating among themselves, but a duty enjoined on them by their God. They had for a long series of years been debarred from the privilege of religious worship, and as there was reason to fear that a continued neglect of divine ordinances would draw down upon them the judgments of offended heaven, they begged permission to go three days' journey into the desert--a place of seclusion--where their sacrificial observances would neither suffer interruption nor give umbrage to the Egyptians. In saying this, they concealed their ultimate design of abandoning the kingdom, and by making this partial request at first, they probably wished to try the king's temper before they disclosed their intentions any farther. But they said only what God had put in their mouths (Exo 3:12, Exo 3:18), and this "legalizes the specific act, while it gives no sanction to the general habit of dissimulation" [CHALMERS].
exo 5:4Wherefore do ye, Moses and Aaron, let the people from their works? &c.--Without taking any notice of what they had said, he treated them as ambitious demagogues, who were appealing to the superstitious feelings of the people, to stir up sedition and diffuse a spirit of discontent, which spreading through so vast a body of slaves, might endanger the peace of the country.
exo 5:6Pharaoh commanded--It was a natural consequence of the high displeasure created by this interview that he should put additional burdens on the oppressed Israelites.
taskmasters--Egyptian overseers, appointed to exact labor of the Israelites.
officers--Hebrews placed over their brethren, under the taskmasters, precisely analogous to the Arab officers set over the Arab Fellahs, the poor laborers in modern Egypt.
exo 5:7Ye shall no more give the people straw to make brick--The making of bricks appears to have been a government monopoly as the ancient bricks are nearly all stamped with the name of a king, and they were formed, as they are still in Lower Egypt, of clay mixed with chopped straw and dried or hardened in the sun. The Israelites were employed in this drudgery; and though they still dwelt in Goshen and held property in flocks and herds, they were compelled in rotation to serve in the brick quarries, pressed in alternating groups, just as the fellaheen, or peasants, are marched by press gangs in the same country still.
let them go and gather straw for themselves--The enraged despot did not issue orders to do an impracticable thing. The Egyptian reapers in the corn harvest were accustomed merely to cut off the ears and leave the stalk standing.
exo 5:8tale--an appointed number of bricks. The materials of their labor were to be no longer supplied, and yet, as the same amount of produce was exacted daily, it is impossible to imagine more aggravated cruelty--a perfect specimen of Oriental despotism.
exo 5:12So the people were scattered--It was an immense grievance to the laborers individually, but there would be no hindrance from the husbandmen whose fields they entered, as almost all the lands of Egypt were in the possession of the crown (Gen 47:20).
exo 5:13And the taskmasters hasted them . . . officers . . . beaten--As the nearest fields were bared and the people had to go farther for stubble, it was impossible for them to meet the demand by the usual tale of bricks. "The beating of the officers is just what might have been expected from an Eastern tyrant, especially in the valley of the Nile, as it appears from the monuments, that ancient Egypt, like modern China, was principally governed by the stick" [TAYLOR]. "The mode of beating was by the offender being laid flat on the ground and generally held by the hands and feet while the chastisement was administered" [WILKINSON]. (Deu 25:2). A picture representing the Hebrews on a brick field, exactly as described in this chapter, was found in an Egyptian tomb at Thebes.
exo 5:20they met Moses . . . The Lord look upon you, and judge--Thus the deliverer of Israel found that this patriotic interference did, in the first instance, only aggravate the evil he wished to remove, and that instead of receiving the gratitude, he was loaded with the reproaches of his countrymen. But as the greatest darkness is immediately before the dawn, so the people of God are often plunged into the deepest affliction when on the eve of their deliverance; and so it was in this case.