Charles Ellicott Commentary Mark 1:23

"And straightway there was in their synagogue a man with an unclean spirit; and he cried out," — Mark 1:23 (ASV)

An unclean spirit.—The phrase occurs in all the first three Gospels (not in St. John’s), but with special frequency in this. As in most Eastern cities, in both ancient and modern times, madness had an immunity from restraint, and the demoniacs seem to have mingled, if they chose, with the crowd of worshippers in the synagogue.