v1 "And afterward Moses and Aaron went in and told Pharaoh, Thus saith the Lord God of Israel, Let my people go that they may hold a feast unto me in the wilderness."
v23 "For since I came to Pharaoh to speak in thy name, he hath done evil to this people; neither hast thou delivered thy people at all.
Wow! That is pretty bold talk from Moses. We do not know the tone of voice so he may have been contrite in his manner.
Pharaoh told Moses that they were just causing the people to leave off their work. He makes what he must have thought to be a very dramatic statement but to me it is very sad. v2 "Who is the Lord, that I should obey his voice to let Israel go? I know not the Lord, neither will I let Israel go."
Pharaoh is a hard case and will need much convincing but he will change his tune about letting Israel leave Egypt. He may not have known the Lord after it was all over but he certainly knew about him and his awesome power.
So Pharaoh increased the workload and made it more difficult to perform by forcing the people to find their own straw instead of providing it as before. In verse 21 the people express their displeasure with Moses and Aaron. "And they said unto them, The Lord look upon you and judge; because ye have made our savor to be abhorred in the eyes of Pharaoh and in the eyes of his servants, to put a sword in their hand to slay us."
In the next chapter God continues to explain to Moses what he is doing and how.
Proverbs 8:15 "By me kings reign, and princes decree justice."