What is the biblical ground for using oil when we pray for healing?

Every week, I answer a common question related to the end times. Today’s is about the biblical ground for using oil when we pray for healing.

Question:

What is the biblical ground for using oil when we pray for healing? Who ordered it? I see oil used in the Old Testament, but I don’t find Jesus giving clear instructions in the New Testament. So why do we still use oil today?