John Lightfoot on Luke 24:37

[They supposed they had seen a spirit.] Whereas the Jews distinguished between angels and spirits and demons; spirits are defined by R. Hoshaniah to be "such to whom souls are created, but they have not a body made for those souls." But it is a question, whether they included all spirits or souls under this notion, when it is more than probable that apparitions of ghosts, or deceased persons who once had a body, were reckoned by them under the same title. Nor do I apprehend the disciples had any other imagination at this time, than that this was not Christ indeed, in his own person, as newly raised from the dead; but a spectrum only in his shape, himself being still dead. And when the Pharisees speak concerning Paul, Acts 23:9, "That if an angel or a spirit had spoken to him," I would easily believe they might mean it of the apparition of some prophet, or some other departed just person, than of any soul that had never yet any body created to it. I the rather incline thus to think, because it is so evident, that it were needless to prove how deeply impressed that nation was with an opinion of the apparitions of departed ghosts.