Our fathers understood not Thy wonders in Egypt… – Psalm 106:7

We find Israel broken down by utter hopelessness. Moses spoke to them again, but we read, “They hearkened not unto Moses for anguish of spirit, and for cruel bondage.” They had been so brutally crushed by the Egyptians, that they had lost all heart. Slavery had killed all the manhood of their race: they were abject, timorous, and crouching bondsmen. The last ounce that breaks the camel’s back was laid on them by Pharaoh, and they could no more listen to words of hope. Moses said he had come to deliver them; he told them they should be brought out with a high hand and an outstretched arm; but they could not think it possible; they shook their heads and turned a deaf ear to what they regarded as vain words. Hope had fled. They understood not that God could, by any possible means, deliver them from the gigantic power which held them down. Alas! this also has been the case with us; and perhaps is the case with some here at this moment. You are so sad and so depressed that you cannot believe in salvation. Your presumptuous hopes lie dead in heaps round about you, and you cannot believe that you will ever be saved. “Oh!” say you, “there may be mercy for anybody else, but there is no mercy for me. God can forgive the chief of sinners, but He will never forgive me.” …You dare not hope that He has ordained you unto eternal life, that He will put His Spirit within you, and that He will give you power to become children of God, and joint-heirs with Christ. Your very sorrow for sin has made you incapable of understanding God’s wonders of grace. This is a painful state of mind.

Was there a single weak point in what God had done for them? They had no ground whatever for their disbelief. O brothers, let us never distrust our God until He gives us ground for so doing; and that will never be. C.H. Spurgeon

https://www.blueletterbible.org/comm/spurgeon_charles/sermons/2204.cfm