"And they do not love you, while you believe in the entire Book," meaning: and they do not believe. There is an implied meaning [within the verse]. "And when they meet you, they say, 'We believe'" out of fear for their blood and their wealth. "And when they are alone, they bite their fingertips at you in rage" because of what they find in their hearts.
God said to His Prophet: "Say, 'Die in your rage,'" up to the end of the verse.