Yahweh asks this rhetorical question to remind Ezekiel something he already knows. The question is a rebuke for the people who use the proverb. Alternate translation: "The people in the land of Israel have this proverb ... 'Fathers eat sour grapes, and the children's teeth are made blunt'." (See: [[rc://en/ta/man/jit/figs-rquestion]])
The idiom "teeth are made blunt" refers to the sour taste in one's mouth that is a result of eating unripe or sour fruit. Alternate translation: "the children get a sour taste in their mouths" (See: [[rc://en/ta/man/jit/figs-idiom]])