According to historians, it was customary at the time this letter was written, for meat that resulted from animal sacrifice to idols to be sold to the public.
We can deduce that Paul was responding to a question like this: "since we know that the gods represented by idols do not exist, what harm is there for the believer to eat such meat, whether at home or in someone else's house?" (See Acts 15:29, 21:25, Revelation 2:20).
It is true that our relationship with God is not influenced by what we eat or stop eating. It is also true that an idol is nothing: there is only one God the Father and one Lord, Jesus Christ.
This we know, but there were then and possibly there are even now many people who believe in idols and give special meaning to the act of eating meat sacrificed to them: some of them converted to Christ, yet take into account this special sense. If they see a Christian eating meat sacrificed to idols, they can be induced to do so as well, to the detriment of their spiritual life because they will be sinning against their conscience. The believer, who by his action leads another to err, sins against Christ even though the action itself is not sin.
We learn, therefore, that our way of proceeding should always take into account the effect it has on others, and we should be guided by our love for them, doing nothing that might offend them and cause them to sin against their conscience.
1 Now concerning things offered to idols: We know that we all have knowledge. Knowledge puffs up, but love edifies. 2 And if anyone thinks that he knows anything, he knows nothing yet as he ought to know. 3 But if anyone loves God, this one is known by Him. 4 Therefore concerning the eating of things offered to idols, we know that an idol is nothing in the world, and that there is no other God but one. 5 For even if there are so-called gods, whether in heaven or on earth (as there are many gods and many lords), 6 yet for us there is one God, the Father, of whom are all things, and we for Him; and one Lord Jesus Christ, through whom are all things, and through whom we live. 7 However, there is not in everyone that knowledge; for some, with consciousness of the idol, until now eat it as a thing offered to an idol; and their conscience, being weak, is defiled. 8 But food does not commend us to God; for neither if we eat are we the better, nor if we do not eat are we the worse. 9 But beware lest somehow this liberty of yours become a stumbling block to those who are weak. 10 For if anyone sees you who have knowledge eating in an idol's temple, will not the conscience of him who is weak be emboldened to eat those things offered to idols? 11 And because of your knowledge shall the weak brother perish, for whom Christ died? 12 But when you thus sin against the brethren, and wound their weak conscience, you sin against Christ. 13 Therefore, if food makes my brother stumble, I will never again eat meat, lest I make my brother stumble.
1 Corinthians chapter 8