Peter was told by the servants of Cornelius why he had sent for him (see Acts 10:22). He knows that he must come to tell him about Jesus Christ. By asking Cornelius this question, he gives him a chance to recount his visit with the angel so that everyone present is on the same page and ready to hear Peter’s message.1
29 So when I was sent for, I came without objection. I ask then why you sent for me.”