For if any man - Any Christian brother who is ignorant, or anyone who might otherwise become a Christian.
Which hast knowledge - Who are fully informed in regard to the real nature of idol worship. You will be looked up to as an example. You will be presumed to be partaking of this feast in honor of the idol. You will thus encourage him, and he will partake of it with a conscientious regard to the idol.
Sit at meat - Sitting down to an entertainment in the temple of the idol. Feasts were often celebrated, as they are now among the pagan, in honor of idols. Those entertainments were either in the temple of the idol, or at the house of him who gave it.
Shall not the conscience of him which is weak - Of the man who is not fully informed, or who still regards the idol with superstitious feelings; see 1 Corinthians 8:7.
Be emboldened - Margin, “Edified” οἰκοδομηθήσεται oikodomēthēsetai. Confirmed; established. So the word “edify” is commonly used in the New Testament; Acts 9:31; Romans 14:19; Ephesians 4:12; 1 Thessalonians 5:11. The sense here is, “Before this he had a superstitious regard for idols. He had the remains of his former feelings and opinions. But he was not established in the belief that an idol was anything; and his superstitious feelings were fast giving way to the better Christian doctrine that they were nothing. But now, by your example, he will be fully confirmed in the belief that an idol is to be regarded with respect and homage. He will see you in the very temple, partaking of a feast in honor of the idol; and he will infer not only that it is right, but that it is a matter of conscience with you, and will follow your example.”