Matthew 21:42 - Ellicott's Commentary On The Whole Bible

Did ye never read....? — The quotation is remarkable as being found (Psalms 118:22) in the immediate context of the verse which had supplied the “hosanna” shouts of the multitude on the preceding day. In the primary meaning of the Psalm, the illustration seems to have been drawn from one of the stones, quarried, hewn, and marked, away from the site of the Temple, which the builders, ignorant of the head architect’s plans, had put on one side, as having no place in the building, but which was found afterwards to be that on which the completeness of the structure depended, that on which, as the chief corner-stone, the two walls met and were bonded together. The Psalmist saw in this a parable of the choice of David to be king over Israel; perhaps, also, of the choice of Israel itself out of the nations of the world. Elsewhere, as in Ephesians 2:20, and in the language of later ages, Christ Himself is the chief corner-stone. Here the context gives a somewhat different application, and “the stone which the builders rejected” is found in the future converts from among the Gentiles, the nation bringing forth the fruits which Israel had not brought forth — the “corner-stone” of the great edifice of the Catholic Church of Christ. This meaning was obviously not incompatible with the other. As the mind of the Psalmist included both David and Israel under the same symbolism, so here the Christ identifies Himself, more or less completely, with the Church which is His body. (Comp. Ephesians 1:22-23.)