Jamieson, Fausset and Brown on 1 Corinthians 12:15

15. The humbler members ought not to disparage themselves, or to be disparaged by others more noble (1Co 12:21, 22).

foot ... hand--The humble speaks of the more honorable member which most nearly resembles itself: so the "ear" of the "eye" (the nobler and more commanding member, Nu 10:31), (1Co 12:16). As in life each compares himself with those whom he approaches nearest in gifts, not those far superior. The foot and hand represent men of active life; the ear and eye, those of contemplative life.