Satan means that if God attacks Job, he will see how Job responds. Alternate translation: "But now, if you stretch out your hand and touch all that he has, you will see that he will curse you to your face"
Here "touch" represents the action of harming or destroying. Alternate translation: "attack all that he has" or "destroy all that he has" (See: [[rc://en/ta/man/jit/figs-metonymy]])