A.T. Robertson Commentary Matthew 22:42

"saying, What think ye of the Christ? whose son is he? They say unto him, [The son] of David." — Matthew 22:42 (ASV)

The Christ (του Χριστου). The Messiah, of course, not Christ as a proper name of Jesus. Jesus here assumes that Ps 110 refers to the Messiah. By his pungent question about the Messiah as David's son and Lord he really touches the problem of his Person (his Deity and his Humanity). Probably the Pharisees had never faced that problem before. They were unable to answer.