Have eaten a sour grape; rather, sour grapes. The prophet (like Ezekiel, Ezekiel 18:1-32.) condemns the use of this proverb, and declares that the sinner is the artificer of his own ruin. At first sight, it may seem as if Jeremiah opposes the second commandment, which describes how God "visits the iniquity of the fathers upon the children" (Exodus 20:5).
This, however, cannot really be, for he endorses this declaration later on (Jeremiah 32:18). The fact is that he is not so much condemning the proverb, as the blasphemous application of it made by the Jews of his time.
It is an eternal truth that sin perpetuates itself (except by the miracles of grace) in the children of transgressors, and intensified sin leads to intensified punishment. But the children of transgressors do not cease to be responsible for their own share in the sin;—this was the truth which Jeremiah's contemporaries ignored.
He does not deny the solidarity of the family or the race,but he superadds the neglected truth of the special responsibility of the individual. This is one among many evidences of the deepening sense of individual life in the later period of the Jewish monarchy.
(A somewhat different view is offered by Delitzsch, 'Messianic Prophecies,' § 50. According to him, Jeremiah looks forward to a time when the individual shall be liberated from the consequences of his solidarity with his race, and when personality shall be "invested with its rights."
But can the individual be thus liberated?