פירוש על עבודה זרה 63:8

The Talmud now asks why one would allow the sale of earthenware flasks but not supporting a bed with the Hadrianic earthenware. The answer is that when it comes to the latter, they are so thoroughly saturated with wine that the prohibited substance is “there.” In contrast, the wine soaked into regular earthenware flasks is not really “there.” It is present in only trace amounts.