Adam Clarke on Matthew 18:1

At the same time - Or hour; but ωρα is frequently used to signify some particular time: however, instead of ωρα, three MSS., all the Itala but four, and Origen, read ημερα, day. Origen says both readings were extant in MSS. in his time.

Who is the greatest - Could these disciples have viewed the kingdom of Christ in any other light than that of a temporal one? Hence they wished to know whom he would make his prime minister - whom his general - whom his chief chancellor - whom supreme judge, etc., etc. Is it he who first became thy disciple, or he who is thy nearest relative, or he who has most frequently entertained thee, or he who is the oldest, merely as to years? Could this inquiry have proceeded from any but the nine disciples who had not witnessed our Lord's transfiguration? Peter, James, and John, were surely more spiritual in their views! And yet how soon did even these forget that his kingdom was not of this world! See Mar 10:35, etc.; Joh 18:10, etc. The disciples having lately seen the keys delivered to Peter, and found that he, with James and John, had been privileged with being present at the transfiguration, it is no wonder if a measure of jealousy and suspicion began to work in their minds. From this inquiry we may also learn, that the disciples had no notion of Peter's supremacy; nor did they understand, as the Roman Catholics will have it, that Christ had constituted him their head, either by the conversation mentioned Mat 16:18, Mat 16:19, or by the act mentioned in the conclusion of the preceding chapter. Had they thought that any such superiority had been designed, their present question must have been extremely impertinent. Let this be observed.