What mean ye, that ye use this proverb concerning the land of Israel, saying, {a} The fathers have eaten sour grapes, and the children's teeth are set on edge?

(a) The people murmured at the chastising of the Lord, and therefore used this proverb meaning that their fathers had sinned and their children were punished for their transgressions. See Geneva Jer 31:29

Wesley's Notes

18:2 The land of Israel - The two tribes, not the ten. The fathers - Our fore - fathers. Have eaten - Have sinned. The childrens - We their children, who were unborn, suffer for their sins.

Jamieson-Fausset-Brown Bible Commentary

2. fathers . eaten sour grapes, . children's teeth . set on edge-Their unbelieving calumnies on God's justice had become so common as to have assumed a proverbial form. The sin of Adam in eating the forbidden fruit, visited on his posterity, seems to have suggested the peculiar form; noticed also by Jeremiah (Jer 31:29); and explained in La 5:7, "Our fathers have sinned, and are not; and we have borne their iniquities." They mean by "the children" themselves, as though they were innocent, whereas they were far from being so. The partial reformation effected since Manasseh's wicked reign, especially among the exiles at Chebar, was their ground for thinking so; but the improvement was only superficial and only fostered their self-righteous spirit, which sought anywhere but in themselves the cause of their calamities; just as the modern Jews attribute their present dispersion, not to their own sins, but to those of their forefathers. It is a universal mark of corrupt nature to lay the blame, which belongs to ourselves, on others and to arraign the justice of God. Compare Ge 3:12, where Adam transfers the blame of his sin to Eve, and even to God, "The woman whom thou gavest to be with me, she gave me of the tree, and I did eat."

Matthew Henry's Concise Commentary

18:1-20 The soul that sinneth it shall die. As to eternity, every man was, is, and will be dealt with, as his conduct shows him to have been under the old covenant of works, or the new covenant of grace. Whatever outward sufferings come upon men through the sins of others, they deserve for their own sins all they suffer; and the Lord overrules every event for the eternal good of believers. All souls are in the hand of the great Creator: he will deal with them in justice or mercy; nor will any perish for the sins of another, who is not in some sense worthy of death for his own. We all have sinned, and our souls must be lost, if God deal with us according to his holy law; but we are invited to come to Christ. If a man who had shown his faith by his works, had a wicked son, whose character and conduct were the reverse of his parent's, could it be expected he should escape the Divine vengeance on account of his father's piety? Surely not. And should a wicked man have a son who walked before God as righteous, this man would not perish for his father's sins. If the son was not free from evils in this life, still he should be partaker of salvation. The question here is not about the meritorious ground of justification, but about the Lord's dealings with the righteous and the wicked.