Take heed that your liberty He leaves their liberty untouched, but moderates the use of it thus far -- that it may not give occasion of stumbling to the weak. And he expressly desires that regard be had to the weak, that is, to those who are not, yet thoroughly confirmed in the doctrine of piety, for as they are wont to be regarded with contempt, it is the will and command of the Lord, that regard should be had to them. In the meantime, he hints that strong giants, who may be desirous tyrannically to subject our liberty to their humor, may safely be let alone, [1] because we need not fear giving offense to those who are not drawn into sin through infirmity, but eagerly catch at something to find fault with. What he means by an occasion, of stumbling we shall see herelong.

Footnotes

1 - "Nous ne nous en devons point soucier, mais les laisser la;" -- "We should not concern ourselves as to them, but leave them there."

But take heed - This is the reply of Paul to the argument of the Corinthians in 1-Corinthians 8:8. "Though all that you say should be admitted to be true, as it must be; though a man is neither morally better nor worse for partaking of meat or abstaining from it; yet the grand principle to be observed is, so to act as not to injure your brethren. Though you may be no better or worse for eating or not eating, yet if your conduct shall injure others, and lead them into sin, that is a sufficient guide to determine you what to do in the case. You should abstain entirely. It is of far more importance that your brother should not be led into sin, than it is that you should partake of meat which you acknowledge 1-Corinthians 8:8 is in itself of no importance."
Lest by any means - μή πως mē pōs. You should be careful that by no conduct of yours your brother be led into sin. This is a general principle that is to regulate Christian conduct in all matters that are in themselves indifferent.
This liberty of yours - This which you claim as a right; this power which you have, and the exercise of which is in itself lawful. The "liberty" or power ἐξουσία exousia here referred to was that of partaking of the meat that was offered in sacrifice to idols; 1-Corinthians 8:8. A man may have a right abstractly to do a thing, but it may not be prudent or wise to exercise it.
Become a stumbling-block - An occasion of sin; see the note at Matthew 5:29; also see the note at Romans 14:13. See that it be not the occasion of leading others to sin, and to abandon their Christian profession; 1-Corinthians 8:10.
To them that are weak - To those professing Christians who are not fully informed or instructed in regard to the true nature of idolatry, and who still may have a superstitious regard for the gods whom their fathers worshipped.

But take heed - Lest by frequenting such feasts and eating things offered to idols, under the conviction that an idol is nothing, and that you may eat those things innocently, this liberty of yours should become a means of grievously offending a weak brother who has not your knowledge, or inducing one who respects you for your superior knowledge to partake of these things with the conscience, the persuasion and belief, that an idol is something, and to conclude, that as you partake of such things, so he may also, and with safety. He is not possessed of your superior information on this point, and he eats to the idol what you take as a common meal.

But take heed lest by any means,.... This is either a reply to the instance of such as argued in favour of eating things offered to idols; or a limitation and explanation of the apostle's own concession, that it made a man, with respect to the favour of God, neither better nor worse: yet care should be taken, lest
this liberty of yours become a stumblingblock to them that are weak; he owns they had a liberty, or a right, or power, as the word may be rendered, of eating, or not eating, as they pleased; but then they ought to be cautious, lest they should be the means of offending, or causing to offend, such who were weak in the faith, and had not that knowledge of Christian liberty they had: not the use of their power and liberty is here denied, but the abuse of it is guarded against; for though the action itself was indifferent, yet as it might be used, it might be sinful, being attended with very bad consequences, such as hereafter mentioned.

this liberty of yours--the watchword for lax Corinthians. The very indifference of meats, which I concede, is the reason why ye should "take heed" not to tempt weak brethren to act against their conscience (which constitutes sin, Romans 14:22-23).