Surely thou didst set them in slippery places - Not in a solid and permanent position; not where their foothold would be secure, but as on smooth and slippery rocks, where they would be liable any moment to fall into the foaming billows. However prosperous their condition may seem to be now, yet it is a condition of uncertainty and danger, from which they must soon fall into ruin. In their prosperity there is nothing of permanence or Stability; and this fact will explain the difficulty.
Thou castedst them down into destruction - They are placed, not in a permanent condition, but in a condition from which they will be cast down to destruction. Ruin is before them; and the end will demonstrate the justice of God. Nothing can be determined from their present condition as to the question which caused so much perplexity, but in order to a proper solution we must wait to see the end. As an illustration of this, see the interesting account of the interview between Solon of Athens, and Croesus, the rich king of Lydia, as given in Herodotus, book i., 30-33.