A.T. Robertson Commentary Matthew 21:42

"Jesus saith unto them, Did ye never read in the scriptures, The stone which the builders rejected, The same was made the head of the corner; This was from the Lord, And it is marvelous in our eyes?" — Matthew 21:42 (ASV)

The stone which (λιθον ον). Inverse attraction of the antecedent into the case of the relative.

The builders rejected (απεδοκιμασαν ο οικοδομουντες). From Ps 118:22. A most telling quotation. These experts in building God's temple had rejected the corner-stone chosen by God for his own house. But God has the last word and sets aside the building experts and puts his Son as the Head of the corner. It was a withering indictment.