Adam Clarke on Luke 9:1

Power and authority - Δυναμιν και εξουσιαν. The words properly mean here, the power to work miracles; and that authority by which the whole demoniac system was to be subjected to them. The reader will please to observe:

1. That Luke mentions both demons and diseases; therefore he was either mistaken, or demons and diseases are not the same.

2. The treatment of these two was not the same: - the demons were to be cast out, the diseases to be healed. See Mat 10:1.