Albert Barnes Commentary 1 Corinthians 10:28

"But if any man say unto you, This hath been offered in sacrifice, eat not, for his sake that showed it, and for conscience sake:" — 1 Corinthians 10:28 (ASV)

But if any man. This refers to any fellow guest, any scrupulous fellow Christian who may be present. That the word "any" (tiv) refers to a fellow guest seems evident. It is not probable that the host would point out any part of the food on his own table if he supposed there was any doubt about the lawfulness of eating it. Yet, a scrupulous fellow Christian might be present who would have strong doubts about the propriety of partaking of the food and would indicate this to the other guests.

For his sake that shewed it. Do not offend him, do not lead him into sin, and do not pain and wound his feelings.

And for conscience sake. Do not eat out of respect for the conscientious scruples of him who told you that it had been offered to idols. The word conscience refers to the conscience of the informer (1 Corinthians 10:29). Still, the believer should make it a matter of conscience not to wound his weak brothers or lead them into sin.

For the earth is the Lord's, etc. (see 1 Corinthians 10:26). These words are missing in many manuscripts (see Mill's Greek Testament) and in the Vulgate, Syriac, Coptic, and Arabic versions, and are omitted by Griesbach. Grotius says that they should be omitted. There might easily have been a mistake in transcribing them from 1 Corinthians 10:26. The authority of the manuscripts, however, favors retaining them, and they are quoted by the Greek fathers and commentators.

If these words are to be retained, they are probably to be interpreted in this sense: "There is no necessity that you should partake of this food. All things belong to God, and he has made ample provision for your wants without subjecting you to the necessity of eating this. Since this is the case, it is best to regard the scruples of those who have doubts about the propriety of eating this food and to abstain."