He destroyed their vines with hail - Margin, killed. See Exodus 9:22-26. In the account in Exodus the hail is said to have smitten man and beast, the herb, and the tree of the field. In the psalm only one thing is mentioned, perhaps denoting the ruin by what would be particularly felt in Palestine, where the culture of the grape was so common and so important.
And their sycamore trees with frost - The sycamore is mentioned particularly as giving poetic beauty to the passage. Of the sycamore tree, Dr. Thomson remarks (“land and the Book,” vol. i. p. 25), “It is a tender tree, flourishes immensely in sandy plains and warm vales, but cannot bear the hard, cold mountain. A sharp frost will kill them; and this agrees with the fact that they were killed by it in Egypt. Among the wonders performed in the field of Zoan, David says, ‘He destroyed their vines with hail, and their sycamores with frost.’ Certainly, a frost keen enough to kill the sycamore would be one of the greatest ‘wonders’ that could happen at the present day in this same field of Zoan.” The word rendered “frost” - חנמל chănâmâl - occurs nowhere else. It is parallel with the word hail in the other member of the sentence, and denotes something that would be destructive to trees. The Septuagint, the Vulgate, and the Arabic render it frost. Gesenius renders it ants.