Yet his meat - His food.
In his bowels is turned - That is, it is as if he had taken food which was exceedingly pleasant, and had retained it in his mouth as long as possible, that he might enjoy it, but when he swallowed it, it became bitter and offensive; compare Revelation 10:9-10. Sin may be pleasant when it is committed, but its consequences will be bitter.
It is the gall of asps - On the meaning of the word here rendered "asps" (פתן pethen), see the notes at Isaiah 11:8. There can be little doubt that the "asp," or aspic, of antiquity, which was so celebrated, is here intended. The bite was deadly, and was regarded as incurable. The sight became immediately dim after the bite - a swelling took place, and pain was felt in the stomach, followed by stupor, convulsions, and death. It is probably the same as the "boetan" of the Arabians. It is about a foot in length, and two inches in circumference - its color being black and white. "Pict. Bib." The word "gall" (מרורה merôrâh), means "bitterness, acridness" (compare Job 13:26); and hence, bile or gall. It is not improbable that it was formerly supposed that the poison of the serpent was contained in the gall, though it is now ascertained that it is found in a small sack in the mouth. It is used here as synonymous with the "poison" of asps - supposed to be "bitter" and "deadly." The meaning is, that sin, however pleasant and grateful it may be when committed, will be as destructive to the soul as food would be to the body, which, as soon as it was swallowed, became the most deadly poison. This is a fair account still of the effects of sin.

Yet his meat in his bowels is turned,.... Or "his bread" (r), to which sin is compared, being what the sinner lives in, and lives upon; what he strengthens himself in and with, and by which he is nourished unto the day of slaughter, and by means of which he grows and proceeds to more ungodliness, though in the issue he comes into starving and famishing circumstances; for this is bread of deceit, and proves to be ashes and gravel stones; it promises pleasure, profit, liberty, and impunity, but is all the reverse; as meat turns in a man's stomach when it does not digest in him, or rather his stomach turns against that, and instead of its being pleasant and agreeable to him, it distresses him and makes him uneasy; sin being compared to meat in the bowels, denotes the finishing of in after it has been conceived in the mind, and completed in the act:
it is the gall of asps within him; which is bitter, though not poison; which yet Pliny (s) suggests, but it seems (t) it is not fact. Sin is an evil and bitter thing, and produces bitter sorrow, and makes bitter work for repentance in good men, Jeremiah 2:19; and fills with distress inexpressible and intolerable in wicked men, as in Cain and Judas in this world, and with black despair, weeping, and gnashing of teeth, and dreadful horrors of conscience, in the world to come, to all eternity; the effect of it is eternal death, the second death, inevitable and everlasting ruin and destruction.
(r) "panis ejus", Pagninus, Montanus, Beza, Schmidt. (s) Nat. Hist. l. 11. c. 37. (t) Scheuchzer. Physic. Sacr. vol. 4. p. 711. Philosoph. Transact. abridged, vol. 2. p. 819.

turned--Hebrew denotes a total change into a disagreeable contrary (Jeremiah 2:21; compare Revelation 10:9-10).
gall--in which the poison of the asp was thought to lie. It rather is contained in a sack in the mouth. Scripture uses popular language, where no moral truth is thereby endangered.

Turned - From sweet to bitter. Gall of asps - Exceeding bitter and pernicious. Gall is most bitter; the gall of serpents is full of poison; and the poison of asps is most dangerous and within a few hours kills without remedy.