And Moses returned unto the LORD, and said, LORD, wherefore hast thou so evil entreated this people? why is it that thou hast sent me?

Wesley's Notes

5:22 He expostulated with him. He knew not how to reconcile the providence with the promise, and the commission he had received. Is this God's coming down to deliver Israel? Must I who hoped to be a blessing to them become a scourge to them? By this attempt to get them out of the pit, they are but sunk the farther into it. Wherefore hast thou so evil entreated this people - Even when God is coming towards his people in ways of mercy, yet sometimes he takes such methods that they may think themselves but ill - treated: when they think so, they should go to God by prayer, and that is the way to have better treatment in God's good time. Why is it that thou hast sent me - Pharaoh has done evil to this people, and not one step seems to be taken towards their deliverance. It cannot but sit very heavy upon the spirits of those whom God employs for him, to see that their labour doth no good, and much more to see that it doth hurt, eventually, though not designedly.

Matthew Henry's Concise Commentary

5:10-23 The Egyptian task-masters were very severe. See what need we have to pray that we may be delivered from wicked men. The head-workmen justly complained to Pharaoh: but he taunted them. The malice of Satan has often represented the service and worship of God, as fit employment only for those who have nothing else to do, and the business only of the idle; whereas, it is the duty of those who are most busy in the world. Those who are diligent in doing sacrifice to the Lord, will, before God, escape the doom of the slothful servant, though with men they do not. The Israelites should have humbled themselves before God, and have taken to themselves the shame of their sin; but instead of that, they quarrel with those who were to be their deliverers. Moses returned to the Lord. He knew that what he had said and done, was by God's direction; and therefore appeals to him. When we find ourselves at any time perplexed in the way of our duty, we ought to go to God, and lay open our case before him by fervent prayer. Disappointments in our work must not drive us from our God, but still we must ponder why they are sent.