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 his bones and his flesh, you will see that he will curse you to your face"
Here "hand" refers to God's power to act. "But now use your power." See how you translated this in [Job 1:11](../01/11.md). (See: [[rc://en/ta/man/translate/figs-metonymy]])