Jamieson, Fausset and Brown on Exodus 5:20-21

20-21. they 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.