1Co 8:10-13 - 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 Messiah died?
12 But when you thus sin against the brethren, and wound their weak conscience, you sin against Messiah.
13 Therefore, if food makes my brother stumble, I will never again eat meat, lest I make my brother stumble.
The subject matter of 1 Corinthians 8 is whether or not it is appropriate to eat food that was offered to idols. The weak brother was one who had not yet overcome the temptation to worship idols. Let's look at these verses in full context:
1Co 8:1-13 - 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 Elohim, 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 Elohim 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 Elohim, the Father, of whom are all things, and we for Him; and one Master Yahushua Messiah, 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 Elohim; 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 Messiah died?
12 But when you thus sin against the brethren, and wound their weak conscience, you sin against Messiah.
13 Therefore, if food makes my brother stumble, I will never again eat meat, lest I make my brother stumble.
If you didn't read the above chapter, please read it fully.
Notice that the strong brother is one who has knowledge that an "idol is nothing" whereas a weak brother is still being faced with temptations that the idol might actually be something deserving of honor or worship. The advice Paul gives in this situation is identical to the advice he gives in Romans 14. Namely, that while an idol is nothing, we should not do anything to cause another person to stumble. Consider the parallel here:
Rom 14:15 - Yet if your brother is grieved because of your food, you are no longer walking in love. Do not destroy with your food the one for whom Messiah died.
1Co 8:11-12 - And because of your knowledge shall the weak brother perish, for whom Messiah died?
12 But when you thus sin against the brethren, and wound their weak conscience, you sin against Messiah.
And again:
Rom 14:21 - It is good neither to eat meat nor drink wine nor do anything by which your brother stumbles or is offended or is made weak.
1Co 8:13 - Therefore, if food makes my brother stumble, I will never again eat meat, lest I make my brother stumble.
So we have almost identical statements coming out of both chapters. The verses in 1 Corinthians are more descriptive in that he is specifically speaking of food offered to idols, but Romans 14 is a bit more vague and open to interpretation.
or this reason, traditional Christianity has taught Romans 14 justifies Sabbath breaking and eating unclean animals.
But lets continue looking at the situation in Corinth and try to get a deeper understanding of Paul's expectations with them:
1Co 10:24-26 - Let no one seek his own, but each one the other's well-being.
25 Eat whatever is sold in the meat market, asking no questions for conscience' sake;
26 for "the earth is Yahweh's, and all its fullness." (quoting Psalm 24:1)