Albert Barnes Commentary Isaiah 38:21

"Now Isaiah had said, Let them take a cake of figs, and lay it for a plaster upon the boil, and he shall recover." — Isaiah 38:21 (ASV)

For Isaiah had said — In the parallel passage in Kings, the statement in these two verses is introduced before the account of the miracle on the sun-dial and before the account of his recovery (2 Kings 20:7–8). The order in which it is introduced, however, is not material.

Let them take a lump of figs — The word used here (דבלה d^ebēlâh) denotes “a round cake” of dried figs pressed together in a mass (1 Samuel 25:18). Figs were pressed together in this way for preservation and for convenience of conveyance.

And lay it for a plaster — The word used here (מרח mârach) properly denotes to rub, bruise, or crush by rubbing; then to rub in, anoint, or soften. Here it means they were to take dried figs and lay them, softened, on the ulcer.

Upon the boil — (משׁחין mash^echı̂yn). This word means a burning sore or an inflamed ulcer (Exodus 9:9, Exodus 9:11; Leviticus 13:18–20). The verb in Arabic means to be hot, inflamed, or to ulcerate. The noun is used to denote a species of black leprosy in Egypt called elephantiasis, which is distinguished by the black scales covering the skin and by the swelling of the legs. Here, it probably denotes a pestilential boil: an eruption, or inflamed ulceration produced by the plague that threatened immediate death.

Jerome says that the plaster of figs was medicinal and adapted to reduce the inflammation and restore health. There is no improbability in this supposition, nor does anything in the narrative prohibit us from supposing that natural means might have been used to restore him. The miracle consisted in the arrest of the shade on the sun-dial and in Isaiah’s announcement that he would recover.

Both Pliny and Celsus assert that dried figs were used in the Materia Medica of the ancients (see Pliny, Natural History 23:7; Celsus, 5:2, quoted by Lowth).