Alma contrasts the ought with the is. The people ought to be his brothers. Instead, they are a “lost and fallen people.” In the middle of these declarations of potential and reality Alma reminds them of the crucial choice before them: Will they repent or not?
Reference: The language is reminiscent of Matthew 3:8: “Bring forth therefore fruits meet for repentance.” Modern English readers may not recognize meet as a form of measure, even though that is the meaning in both the King James English and in the Book of Mormon. It was probably archaic for Joseph Smith as well, though less distant, since Webster’s 1828 dictionary lists it in the entry for “measure”:
MEASURE, n. mezh’ur. French mesure; Italian misura; Spanish medida; Armoric musur or musul; Irish meas; Welsh meidyr and mesur; German mass, measure, and messen, to measure; Dutch maat; Swedish matt; Danish maade, measure, and mode; Latin mensura, from mensus, with a casual n, the participle of metior, to measure, to mete; Greek. With these correspond the meet, fit, proper, and meet, the verb; Saxon gemet, meet, fit; metan and gemettan, to meet or meet with, to find, to mete or measure, and to paint. The sense is to come to, to fall, to happen, and this sense is connected with that of stretching, extending, that is, reaching to; the latter gives the sense of measure. We find in Hebrew measure; to mete, to measure. This word in Arabic madda, signifies to stretch or extend, to draw out in length or time; as do other verbs with the same elements, under one of which we find the meta of the Latins. The Chaldee signifies to come to, to arrive, to reach, to be mature, and, in Hebrew, Chaldee and Ethiopic signifies to find, to come to. Now the Saxon verb unites in itself the significations of all three of the oriental verbs.
With this background, what does “works which are meet for repentance” mean? They are works that are sufficient for repentance—work that, when measured against the need for repentance, fulfill the requirement. This concept tells us that repentance is not a simple process and that different circumstances might require different types, intensities, or processes of repentance. (See “Excursus: The Principle of Repentance,” following 3 Nephi 18.) A simple “excuse me” may be sufficient repentance for a social faux pas but terribly insufficient for a violation of the law of chastity.