My question is on the anointing oil referred to in James 5:14. What do you make of the olive oil the Pentecostals use to anoint different things including buildings? They always quote James 5 to substantiate their claim. Who prepared this oil in James 5 or what is its origin? If there is a group of elders in need of it for use in their congregation, where will they get it from?
We do not know who prepared this oil referred to in James 5. I assume that it was just plain old oil–almost certainly olive oil. If I am right, then there was no "preparing" done at all. Any oil bought in the market would do the trick. The idea of having specially blessed holy oil with mystical power of its own–imparted by a priest–is from a more superstitious time such as with the Greek Orthodox or Roman Catholic Church when the idea of a sacrament had been developed. I see no reason to believe that the church saw any actual mystical power in the oil itself in the context of James 5:14. The power was in the prayer. The elders were called upon to do this because, as shepherds, their particular ministry was to the needs, including the health needs of the saints. Apparently, the early church saw one of the roles of the elders (who were normally the house church leaders) was to offer prayer over the sick and to do a symbolic ceremony of anointing with oil. Many ancients saw the oil as having medicinal properties. Whether or not the oil mentioned in James 5:14 was for purely medicinal purposes, or whether there was a ceremonial aspect to emphasize the purely spiritual power of prayer is not completely clear. In my opinion, the oil was part of a ceremonial praying for the recovery of the sick, as well as a prayer for forgiveness for sins committed, but I would not deny that there may have been a medicinal property in mind as well.
How this applies to Pentecostals today is not clear. Probably those of us who are not Pentecostals should consider not worrying about what they are doing. It is their business. In the church I am part of, we tend to downplay spiritual healing. I believe we may do so to a fault. Maybe the Pentecostals have something to teach us in this area. Given that we know the elders were doing this in the first century, it seems questionable to criticize Pentecostals for repeating the ceremony of anointing oil for those who are sick. As for anointing oil for a new building or a business or a marriage or whatever… This is clearly not prescribed in James 5. Praying for the sick and those who were sick because of sins in their lives is the context of James 5:14.
My answer to how we should think about the Pentecostal practice will depend on the reason for your question. Are you asking whether you or the church of which you are a member ought to also be anointing buildings with oil? I say there is no biblical reason for you to do this. This a tradition and there is no biblical imperative for you to adopt this tradition. Should you be calling the elders to bring oil and anoint a sick person? That is debatable. Perhaps the modern equivalent of asking the church to pray for the person is sufficient. I am not convinced that the oil itself was necessary to the blessing brought by the prayer of the righteous person in James 5:14, but I can see no harm in incorporating this practice into the modern church. If you are asking if it is somehow "bad" or "unscriptural" to anoint a building with oil to bless the building, my response is that this is not a biblical thing to do, but I feel I have better things to do than to criticize a debatable practice such as this. I would not take part in or encourage such a ceremony (to me personally, it is too closely associated with some unbiblical practices of Pentecostals, but that is a personal, emotional response), but I feel it is not my business particularly that others do this. I do not see it as a dangerous or destructive false doctrine. That seems to be overreacting to me. There is no reason for me to pass judgment on this practice, even if I do not see a need for it.
Sorry to give a somewhat ambiguous response to your question.