John Wesley on Mark 6:13

They anointed with oil many that were sick - Which St. James gives as a general direction, Jas 5:14,15, adding those peremptory words, And the Lord shall heal him - He shall be restored to health: not by the natural efficacy of the oil, but by the supernatural blessing of God. And it seems this was the great standing means of healing, desperate diseases in the Christian Church, long before extreme unction was used or heard of, which bears scarce any resemblance to it; the former being used only as a means of health; the latter only when life is despaired of.