Why did the Jews understand the wine-and-water imagery in Isaiah 1:22?
Because wine and water were part of their everyday experience, the imagery was simple enough for a child to grasp. They knew water diluted wine, especially expensive wine, making it worthless, so they recognized the picture of corrupting something valuable.
Les explains that Isaiah 1:22 uses simple, everyday language that even children can understand. The Jews understood it because wine was part of their ordinary experience. Watering down wine, especially an expensive French wine, leaves something not worth swallowing. The underlying point was that somebody was corrupting them, which Paul also addresses in Galatians when he speaks of his spiritual commission.
Isaiah 1:22
Thy silver is become dross, thy wine mixed with water: