Albert Barnes on Mark 6:13

Cast out many devils. Mt 4:24.

And anointed with oil, etc. Anointing with oil was in common use among the Jews in cases of sickness. It was supposed to have a mild, soothing, and alleviating effect on the body. In Jas 5:14, the elders of the church, in connexion with prayers, were directed also to anoint the sick with oil. It was also used in wounds. The good Samaritan poured in oil and wine into the wounds of the waylaid Jew, Lk 10:34. Josephus says, that in the last sickness of Herod, his physicians commanded him to be anointed with oil. It need not be supposed, however, that the apostles used oil for mere medical purposes. It was used, probably, like the imposition of hands, or like our Saviour's anointing the eyes of the blind with clay, merely as a sign, in expectation of imparting that aid and comfort from God which was sought, and which was represented by the natural, soothing, and gentle effect of oil.

(g) "many devils" Lk 10:17 (h) "oil" Jas 5:14