Not Understanding God’s Actions Responding to Satan

Why did God respond this way to Satan? I don’t understand this.

Job 2:4-7 NLT

“Satan replied to the Lord, “Skin for skin! A man will give up everything he has to save his life. But reach out and take away his health, and he will surely curse you to your face!” “All right, do with him as you please,” the Lord said to Satan. “But spare his life.” So Satan left the Lord’s presence, and he struck Job with terrible boils from head to foot.”

See it at YouVersion.com:

http://bible.us/Job2.4.NLT