A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
1 Corinthians 8:1
co1 8:1ON PARTAKING OF MEATS OFFERED TO IDOLS. (Co1 8:1-13)
Though to those knowing that an idol has no existence, the question of eating meats offered to idols (referred to in the letter of the Corinthians, compare Co1 7:1) might seem unimportant, it is not so with some, and the infirmities of such should be respected. The portions of the victims not offered on the altars belonged partly to the priests, partly to the offerers; and were eaten at feasts in the temples and in private houses and were often sold in the markets; so that Christians were constantly exposed to the temptation of receiving them, which was forbidden (Num 25:2; Psa 106:28). The apostles forbade it in their decree issued from Jerusalem (Acts 15:1-29; Act 21:25); but Paul does not allude here to that decree, as he rests his precepts rather on his own independent apostolic authority.
we know that we all have knowledge--The Corinthians doubtless had referred to their "knowledge" (namely, of the indifference of meats, as in themselves having no sanctity or pollution). Paul replies, "We are aware that we all have [speaking generally, and so far as Christian theory goes; for in Co1 8:7 he speaks of some who practically have not] this knowledge."
Knowledge puffeth up--when without "love." Here a parenthesis begins; and the main subject is resumed in the same words, Co1 8:4. "As concerning [touching] therefore the eating," &c. "Puffing up" is to please self. "Edifying" is to please one's neighbor; Knowledge only says, All things are lawful for me; Love adds, But all things do not edify [BENGEL], (Co1 10:23; Rom 14:15).
edifieth--tends to build up the spiritual temple (Co1 3:9; Co1 6:19).
1 Corinthians 8:2
co1 8:2And--omitted in the oldest manuscripts The absence of the connecting particle gives an emphatical sententiousness to the style, suitable to the subject. The first step to knowledge is to know our own ignorance. Without love there is only the appearance of knowledge.
knoweth--The oldest manuscripts read a Greek word implying personal experimental acquaintance, not merely knowledge of a fact, which the Greek of "we know" or are aware (Co1 8:1) means.
as he ought to know--experimentally and in the way of "love."
1 Corinthians 8:3
co1 8:3love God--the source of love to our neighbor (Jo1 4:11-12, Jo1 4:20; Jo1 5:2).
the same--literally, "this man"; he who loves, not he who "thinks that he knows," not having "charity" or love (Co1 8:1-2).
is known of him--is known with the knowledge of approval and is acknowledged by God as His (Psa 1:6; Gal 4:9; Ti2 2:19). Contrast, "I never knew you" (Mat 7:23). To love God is to know God; and he who thus knows God has been first known by God (compare Co1 13:12; Pe1 1:2).
1 Corinthians 8:4
co1 8:4As concerning, &c.--resuming the subject begun in Co1 8:1, "As touching," &c.
idol is nothing--has no true being at all, the god it represents is not a living reality. This does not contradict Co1 10:20, which states that they who worship idols, worship devils; for here it is the GODS believed by the worshippers to be represented by the idols which are denied to have any existence, not the devils which really under the idols delude the worshippers.
none other God--The oldest manuscripts omit the word "other"; which gives a clearer sense.
1 Corinthians 8:5
co1 8:5"For even supposing there are (exist) gods so called (Th2 2:4), whether in heaven (as the sun, moon, and stars) or in earth (as deified kings, beasts, &c.), as there be (a recognized fact, Deu 10:17; Psa 135:5; Psa 136:2) gods many and lords many." Angels and men in authority are termed gods in Scripture, as exercising a divinely delegated power under God (compare Exo 22:9, with Exo 22:28; Psa 82:1, Psa 82:6; Joh 10:34-35).
1 Corinthians 8:6
co1 8:6to us--believers.
of whom--from whom as Creator all things derive their existence.
we in him--rather, "we for Him," or "unto Him." God the FATHER is the end for whom and for whose glory believers live. In Col 1:16 all things are said to be created (not only "by" Christ, but also) "for Him" (CHRIST). So entirely are the Father and Son one (compare Rom 11:36; Heb 2:10).
one Lord--contrasted with the "many lords" of heathendom (Co1 8:5).
by whom-- (Joh 1:3; Heb 1:2).
we by him--as all things are "of" the Father by creation, so they (we believers especially) are restored to Him by the new creation (Col 1:20; Rev 21:5). Also, as all things are by Christ by creation, so they (we especially) are restored by Him by the new creation.
1 Corinthians 8:7
co1 8:7Howbeit--Though to us who "have knowledge" (Co1 8:1, Co1 8:4-6) all meats are indifferent, yet "this knowledge is not in all" in the same degree as we have it. Paul had admitted to the Corinthians that "we all have knowledge" (Co1 8:1), that is, so far as Christian theory goes; but practically some have it not in the same degree.
with conscience--an ancient reading; but other very old manuscripts read "association" or "habit." In either reading the meaning is: Some Gentile Christians, whether from old association of ideas or misdirected conscience, when they ate such meats, ate them with some feeling as if the idol were something real (Co1 8:4), and had changed the meats by the fact of the consecration into something either holy or else polluted.
unto this hour--after they have embraced Christianity; an implied censure, that they are not further advanced by this time in Christian "knowledge."
their conscience . . . is defiled--by their eating it "as a thing offered to idols." If they ate it unconscious at the time that it had been offered to idols, there would be no defilement of conscience. But conscious of what it was, and not having such knowledge as other Corinthians boasted of, namely, that an idol is nothing and can therefore neither pollute nor sanctify meats, they by eating them sin against conscience (compare Rom 14:15-23). It was on the ground of Christian expediency, not to cause a stumbling-block to "weak" brethren, that the Jerusalem decree against partaking of such meats (though indifferent in themselves) was passed (Acts 15:1-29). Hence he here vindicates it against the Corinthian asserters of an inexpedient liberty.
1 Corinthians 8:8
co1 8:8Other old manuscripts read, "Neither if we do not eat, are we the better: neither if we eat are we the worse": the language of the eaters who justified their eating thus [LACHMANN]. In English Version Paul admits that "meat neither presents [so the Greek for 'commendeth'] us as commended nor as disapproved before God": it does not affect our standing before God (Rom 14:6).
1 Corinthians 8:9
co1 8:9this liberty of yours--the watchword for lax Corinthians. The very indifference of meats, which I concede, is the reason why ye should "take heed" not to tempt weak brethren to act against their conscience (which constitutes sin, Rom 14:22-23).
1 Corinthians 8:10
co1 8:10if any man--being weak.
which hast knowledge--The very knowledge which thou pridest thyself on (Co1 8:1), will lead the weak after thy example to do that against his conscience, which thou doest without any scruple of conscience; namely, to eat meats offered to idols.
conscience of him which is weak--rather, "His conscience, seeing he is weak" [ALFORD and others].
emboldened--literally, "built up." You ought to have built up your brother in good: but by your example your building him up is the emboldening him to violate his conscience.
1 Corinthians 8:11
co1 8:11shall . . . perish--The oldest manuscripts read "perisheth." A single act seemingly unimportant may produce everlasting consequences. The weak brother loses his faith, and if he do not recover it, his salvation [BENGEL] (Rom 14:23).
for whom Christ died--and for whose sake we too ought to be willing to die (Jo1 3:16). And yet professing Christians at Corinth virtually tempted their brethren to their damnation, so far were they from sacrificing aught for their salvation. Note here, that it is no argument against the dogma that Christ died for all, even for those who perish, to say that thus He would have died in vain for many. Scripture is our rule, not our suppositions as to consequences. More is involved in redemption than the salvation of man: the character of God as at once just and loving is vindicated even in the case of the lost for they might have been saved, and so even in their case Christ has not died in vain. So the mercies of God's providence are not in vain, though many abuse them. Even the condemned shall manifest God's love in the great day, in that they too had the offer of God's mercy. It shall be the most awful ingredient in their cup that they might have been saved but would not: Christ died to redeem even them.
1 Corinthians 8:12
co1 8:12wound their weak conscience--literally, "smite their conscience, being (as yet) in a weak state." It aggravates the cruelty of the act that it is committed on the weak, just as if one were to strike an invalid.
against Christ--on account of the sympathy between Christ and His members (Mat 25:40; Act 9:4-5).
1 Corinthians 8:13
co1 8:13meat--Old English for "food" in general.
make . . . to offend--Greek, "is a stumbling-block to."
no flesh--In order to ensure my avoiding flesh offered to idols, I would abstain from all kinds of flesh, in order not to be a stumbling-block to my brother.