Albert Barnes Commentary 1 Corinthians 8:7

"Howbeit there is not in all men that knowledge: but some, being used until now to the idol, eat as [of] a thing sacrificed to an idol; and their conscience being weak is defiled." — 1 Corinthians 8:7 (ASV)

Howbeit. But. In the previous verses, Paul had stated the argument of the Corinthians—that they all knew that an idol was nothing; that they worshipped but one God; and that there could be no danger of their falling into idolatry, even should they partake of the meat offered in sacrifice to idols. Here he replies that though this might be generally true, it was not universally so; for some were ignorant on this subject and supposed that an idol had a real existence, and that to partake of that meat would be to confirm them in their superstition. The inference therefore is, that on their account, they should abstain. See 1 Corinthians 8:11–13.

There is not, etc. There are some who are weak and ignorant; who still have remains of heathen opinions and superstitious feelings.

That knowledge. That there is but one God, and that an idol is nothing.

For some, with conscience of the idol. From conscientious regard to the idol; believing that an idol god has a real existence, and that his favor should be sought, and his wrath be deprecated. It is not to be supposed that converted people would regard idols as the only God; but they might suppose that they were intermediate beings, good or bad angels, and that it was proper to seek their favor or avert their wrath. We are to bear in mind that the heathen were exceedingly ignorant; and that their former notions and superstitious feelings about the gods whom their fathers worshipped, and whom they had adored, would not quickly leave them, even on their conversion to Christianity.

This is just one instance, like thousands, in which former erroneous opinions, prejudices, or superstitious views may influence those who are truly converted to God, and greatly mar and disfigure the beauty and symmetry of their religious character.

Eat it as a thing, etc. As offered to an idol who was entitled to adoration; or as having a right to their homage. They supposed that some invisible spirit was present with the idol, and that his favor should be sought, or his wrath averted, by sacrifice.

And their conscience being weak. Being unenlightened on this subject, and being too weak to withstand the temptation in such a case. Not having a conscience sufficiently clear and strong to enable them to resist the temptation, to overcome all their former prejudices and superstitious feelings, and to act in an independent manner, as if an idol were nothing.

Or their conscience was morbidly sensitive and delicate on this subject: they might be disposed to do right, and yet not have sufficient knowledge to convince them that an idol was nothing, and that they ought not to regard it.

Is defiled. Polluted; contaminated. By thus countenancing idolatry he is led into sin and contracts guilt that will give him pain when his conscience becomes more enlightened (1 Corinthians 8:11, 13). From superstitious reverence of the idol, he might think that he was doing right; but the effect would be to lead him to a conformity to idol worship that would defile his conscience, pollute his mind, and ultimately produce the deep and painful conviction of guilt.

The general reply, therefore, of Paul to the first argument in favor of partaking of the meat offered in sacrifice to idols is that all Christians do not have full knowledge on the subject, and that to partake of that meat might lead them into the sin of idolatry, and corrupt and destroy their souls.