Albert Barnes Commentary 2 Kings 9:1

"And Elisha the prophet called one of the sons of the prophets, and said unto him, Gird up thy loins, and take this vial of oil in thy hand, and go to Ramoth-gilead." — 2 Kings 9:1 (ASV)

Box - Rather, “flask,” or “vial” (1 Samuel 10:1). Oil and ointment were commonly kept in open-mouthed jars, vases, or bottles made of glass, alabaster, or earthenware. Many such vessels have been found in both Egypt and Assyria. The “oil” was the holy oil, compounded according to the formula given in Exodus 30:23-25.