John Calvin Commentary Exodus 6:1

"And Jehovah said unto Moses, Now shalt thou see what I will do to Pharaoh: for by a strong hand shall he let them go, and by a strong hand shall he drive them out of his land." — Exodus 6:1 (ASV)

Then the Lord said to Moses. Moses was indeed unworthy of receiving so kind and gentle a reply from God; but the Father of all goodness, out of His infinite mercy, pardoned both the sins of Moses and of the people, so that He might accomplish the deliverance which He had determined. Yet He presents nothing new, but repeats and confirms His former declaration, that Pharaoh would not obey until forcibly compelled to do so.

The expression, you shall see, is a tacit reproof of his immoderate impatience, in not waiting for the result of the promise. The reason is then added why God is unwilling that His people should be spontaneously dismissed by the tyrant, namely, because He wished the work of their liberation to be conspicuous.

We must remark the strength of the words drive them out; as if He had said that when Pharaoh had been subdued and routed in the contest, he would not only consent, but would consider it a great blessing for the people to depart as quickly as possible. The sum is that he who today refuses to let you depart will not only set you free, but will even expel you from his kingdom.