How is he his son? - As the Jews did not attempt to deny the conclusion of our Lord's question, which was, the Messiah is not only the son of David according to the flesh, but he is the Lord of David according to his Divine nature, then it is evident they could not. Indeed, there was no other way of invalidating the argument, but by denying that the prophecy in question related to Christ: but it seems the prophecy was so fully and so generally understood to belong to the Messiah that they did not attempt to do this; for it is immediately added, No man was able to answer him a word - they were completely nonplussed and confounded.

how.

John 8:58 Jesus said to them, Truly, truly, I say to you, Before Abraham was, I am.

Romans 1:3,4 Concerning his Son Jesus Christ our Lord, which was made of the seed of David according to the flesh...

Romans 9:5 Whose are the fathers, and of whom as concerning the flesh Christ came, who is over all, God blessed for ever. Amen.

Philippians 2:6-8 Who, being in the form of God, thought it not robbery to be equal with God...

1 Timothy 3:16 And without controversy great is the mystery of godliness: God was manifest in the flesh, justified in the Spirit, seen of angels...

Hebrews 2:14 For as much then as the children are partakers of flesh and blood, he also himself likewise took part of the same...

Revelation 22:16 I Jesus have sent my angel to testify to you these things in the churches. I am the root and the offspring of David...

On the Same Words of the Gospel, Matt. xxii. 42
1. The question which was proposed to the Jews, Christians ought to solve. For the Lord Jesus Christ, who proposed it to the Jews, did not solve it Himself, to the Jews, I mean, He did not, but to us He hath solved it. I will put you in remembrance, Beloved, and ye will find that He hath solved it. But first consider the knot of the question. He asked the Jews what they "thought of Christ, whose Son He was to be;" for they too look for the Christ. They read of Him in the Prophets, they expected Him …
Saint Augustine—sermons on selected lessons of the new testament

The Heavenly Banquet.
20th Sunday after Trinity. S. Matt. xxii. 4. "Behold, I have prepared my dinner; my oxen and my fatlings are killed, and all things are ready; come unto the marriage." INTRODUCTION.--The Kingdom of Heaven has two meanings in this parable. It means in the first place the Catholic Church. Into that the apostles and pastors of Christ invite men to enter, and many refuse. In the second place it means the Church Triumphant,--eternal blessedness, and into that the pastors of Christ's Church invite you …
S. Baring-Gould—The Village Pulpit, Volume II. Trinity to Advent

Profession and Practice.
18th Sunday after Trinity. S. Matt. xxii. 42. "What think ye of Christ?" INTRODUCTION.--Many men are Christians neither in understanding nor in heart. Some are Christians in heart, and not in understanding. Some in understanding, and not in heart, and some are Christians in both. If I were to go into a Temple of the Hindoos, or into a Synagogue of the Jews, and were to ask, "What think ye of Christ?" the people there would shake their heads and deny that He is God, and reject His teaching. The …
S. Baring-Gould—The Village Pulpit, Volume II. Trinity to Advent