Matthew 21:37

By the Son sent at last, is denoted the advent of our Lord.

And wherefore sent He not His Son immediately? In order that they might condemn themselves for the things done to the others, and leave off their wrath, and reverence Him when He came. There are also other reasons, but for the present let us go on to what is next. But what means, "It may be they will reverence?" It is not the language of one ignorant, away with the thought! but of one desiring to show the sin to be great; and without any excuse. Since Himself knowing that they would slay Him, He sent Him. But He saith, "They will reverence," declaring what ought to have been done, that it was their duty to have reverenced Him. Since elsewhere also He saith, "if perchance they will hear;" not in this case either being ignorant, but lest any of the obstinate should say, that His prediction was the thing that necessitated their disobedience, therefore He frames His expressions in this way, saying, "Whether they will," and, "It may be." For though they had been obstinate towards His servants, yet ought they to have reverenced the dignity of the Son.

But when He says, They will reverence my Son, He does not speak as in ignorance. For what is there that this householder (by whom in this place God is intended) knows not? But God is thus spoken of as being uncertain, in order that free-will may be reserved for man. Let us enquire of Arrius and Eunomius. See here the Father is said not to know somewhat. Whatever answer they make for the Father, let them understand the same of the Son, when He says that He knows not the day of the consummation of all things. (Mat. 22:36.)

He sent Him not as the bearer of a sentence of punishment against the guilty, but of an offer of repentance; He sent Him to put them to shame, not to punish them. But some say, that it was after His incarnation, that Christ was called a Son in right of His baptism like the other saints, whom the Lord refutes by this place, saying, I will send my Son. Therefore when He thus meditated sending His Son after the Prophets, He must have been already His Son. Further, if He had been His Son in the same way as all the saints to whom the word of God was sent, He ought to have called the Prophets also His sons, as He calls Christ, or to call Christ His servant, as He calls the Prophets.

Morally; a vineyard has been let out to each of us to dress, when the mystery of baptism was given us, to be cultivated by action. Servants one, two, and three are sent us when Law, Psalm, and Prophecy are read, after whose instructions we are to work well. He that is sent is beaten and cast out when the word is contemned, or, which is worse, is blasphemed. He kills (as far as in him lies) the heir, who tramples under foot the Son, and does despite to the Spirit of grace. The wicked husbandman is destroyed, and the vineyard is given to another, when the gift of grace which the proud has contemned is given to the lowly.