What does Paul say he will give up if his eating causes his brother to stumble?
Paul says he will eat no flesh as long as the world stands if meat causes his brother to offend. He refuses to use his liberty in a way that wounds a weak believer's conscience, choosing instead to forgo eating meat so he does not make his brother stumble.
Les teaches that in verse 13 Paul says, "Wherefore if meat makes my brother to offend, I will eat no flesh, while the world standeth, lest I make my brother to offend." Les notes this is basically what Paul said back in Romans: if something does not hurt a mature believer but bothers the weak believer, then for his sake, don't do it. Wounding their weak conscience is sinning against Christ, so believers must watch out for the weak brother.
Wherefore, if meat make my brother to offend, I will eat no flesh while the world standeth, lest I make my brother to offend.