Jesus asked this to prepare His disciples for insults before they came. He had just said, "The disciple is not above his master" (Matthew 10:24). Barnes sums it up: "you must expect the same treatment which I have received." The question argues from the greater to the lesser: if His enemies slandered the head of the house, they would surely slander His household. Gill says Christ is master of the family "both in heaven and in earth," and if He was called by "the most opprobrious names," those of lower rank in His family should expect the same.

The answer is plain: if the master was called Beelzebub, His household can expect the same. Jesus did not wait for a reply but turned straight to comfort: "Fear them not therefore: for there is nothing covered, that shall not be revealed" (Matthew 10:26). He told them to speak in the light what He told them in darkness, to fear God rather than those who can only kill the body, and to trust the Father who watches even the sparrows (Matthew 10:27-31).

Beelzebub was the name of a false god. In 2 Kings 1:2, King Ahaziah sent to inquire of "Baal-zebub the god of Ekron." Barnes says the name "literally means 'the god of flies.'" He adds that the correct reading in the Gospels is thought to be "Beelzebul," which he explains as an Aramean form meaning "god of dung" or "filth." Gill notes that "Beelzebul" is commonly rendered "lord of dung," but he himself would rather take it to mean "the lord of the heavens." The ESV uses "Beelzebul." Barnes concludes: "By giving the name to Christ, they poured upon him the greatest possible abuse and contempt."

Jesus speaks as if the slander had already happened. Earlier in Matthew the Pharisees said, "He casteth out devils through the prince of the devils" (Matthew 9:34). Later they would name Beelzebub outright (Matthew 12:24). "Master of the house" is the Greek oikodespotes, the head of a household.

This question shows how closely Jesus ties His followers to Himself. He calls them "his household" (Matthew 10:25). They belong to His family, so they share His name, and also the insults aimed at it. Being treated like Jesus is not a sign that something has gone wrong; it is part of belonging to Him.

Jesus surrounds this hard word with comfort. Right after it, He says three times not to fear (Matthew 10:26, 28, 31), and He promises that the Father cares even for sparrows. Later He would say it again: "The servant is not greater than his lord. If they have persecuted me, they will also persecute you" (John 15:20).