1 Corinthians 12:15

This however he states last; but for the present he goes to the members themselves, saying thus: "If the foot shall say, Because I am not the hand, I am not of the body; is it therefore not of the body?" "And if the ear shall say, Because I am not the eye, I am not of the body; is it therefore not of the body?" For if the one being made inferior and the other superior, doth not allow their being of the body, the whole is done away. Do not say therefore, "I am not the body, because I am inferior." For the foot also hath the inferior post, yet is it of the body: for the being or not being part of the body, is not from the one lying in this place and the other in that; (which is what constitutes difference of place;) but from the being conjoined or separated. For the being or not being a body, arises from the having been made one or not. But do thou, I pray, mark his considerate way, how he applies their words to our members. For as he said above, "These things have I in a figure transferred to myself and Apollos," just so likewise here, to make his argument free from invidiousness and acceptable, he introduces the members speaking: that when they shall hear nature answering them, being thus convicted by experience herself and by the general voice, they may have nothing further to oppose. "For say, if you will," saith he, "this very thing, murmur as you please, you cannot be out of the body. For as the law of nature, so much more doth the power of grace guard all things and preserve them entire." And see how he kept to the rule of having nothing superfluous; not working out his argument on all the members, but on two only and these the extremes; having specified both the most honorable of all, the eye, and the meanest of all, the feet. […]

This means that a weak brother cannot say that he is not a part of the body simply because he is not strong.

Then when he says: If the foot should say, he clarifies what he had said by using certain members as examples. First, the members involved in motion, and he mentions two members: the foot as the more ignoble member in that it treads the earth …

So among men each is apt to compare himself with those whose gifts some way resemble his own, rather than with those who are at a distance, either above or beneath him. Is it therefore not of the body - Is the inference good? Perhaps the foot may represent private Christians; the hand, officers in the church; the eye, teachers; the ear, hearers.

Shall it hereupon disown relation to the body? Because it is not fixed in the same station, or favoured with the same gifts as others, shall it say, "I do not belong to Christ?" No, the meanest member of his body is as much a member as the noblest, and as truly regarded by him. All his members are dear to him.