Unclean spirits - Persons who were possessed of evil spirits.
Thou art the Son of God - The Son of God, by way of eminence. In this place it is equivalent to the Messiah, who was, among the Jews, called the Son of God. Hence, they were charged not to make him known, because he was not desirous that it should be blazoned abroad that he claimed to be the Messiah. He had not yet done what he wished in order to establish his claims to the Messiahship. He was poor and unhonored, and the claim would be treated as that of an impostor. “For the present,” therefore, he did not wish that it should be proclaimed abroad that he was the Messiah. The circumstance here referred to demonstrates the existence of evil spirits. If these were merely diseased or deranged persons, then it is strange that they should be endowed with knowledge so much superior to those in health. If they were under the influence of an order of spirits superior to man - whose appropriate habitation was in another world - then it is not strange that they should know him, even in the midst of his poverty, to be the Messiah, the Son of God.