John Gill Commentary 1 Kings 18:33

"And he put the wood in order, and cut the bullock in pieces, and laid it on the wood. And he said, Fill four jars with water, and pour it on the burnt-offering, and on the wood." — 1 Kings 18:33 (ASV)

And he put the wood in order, and cut the bullock in pieces, and laid him on the wood Just in such manner as sacrifices usually were:

and said, fill four barrels with water; either from the brook Kishon, or, if that was dried up, from the sea; for both were near this mountain, and so to be had, though a time of drought:

and pour it on the burnt sacrifice; that which was intended to be one:

and upon the wood: wherewith it was to be burnt, and so made unfit for it; and which would make the miracle appear the greater, when fire came down and consumed it.