From Purchas His Pilgrims, Book 4, Chapter 2, Of the Medes, we have an example of flaming arrows being used against humans, rather than as mere incendiaries to ignite buildings and ships.

In this Region was made the oile Medicum, wherein their arrowes were steeped, which being shot out of a looser bow (for a swifter shot extinguished it) did burne the flesh in which it did sticke, and if water were applied to it, the fire thereof encreased. Nor could any remedy cure the same, but hurling dust thereon. It was composed of Naphta.