Sforno on Deuteronomy 32:33/ספורנו על דברים ל״ב:ל״ג

1חמת תנינים יינם, their wine is the venom of asps; among the clusters mentioned in verse 32 there are also poisonous grapes, hidden and unidentifiable among the grapes. This disaster awaits them as a manifestation of the attribute of Justice they have richly deserved. Until they actually are extracting the juice from these grapes [this is all hyperbole, of course, Ed.] G’d did not convert His threat of retribution into something actual. Compare Isaiah 63,3, G’d saying that He alone squeezed out these grapes by treading on them.