For because there are many who show mercy, and who commit no rapine, nor are covetous, who yet are guilty of fornication and uncleanness; to signify that the former alone suffices not, He has added this, much in the same sense as Paul, writing to the Corinthians, bore witness of the Macedonians, that they were rich not only in almsgiving, but also in all other virtue. For having spoken of the noble spirit they had shown in regard of their goods, he says, “They gave also their own selves to the Lord, and to us.”
7. “Blessed are the peace-makers.”
Here He not only takes away altogether our own strife and hatred among ourselves, but He requires besides this something more, namely, that we should set at one again others, who are at strife.
And again, the reward which He annexes is spiritual. Of what kind then is it.
“For they shall be called the children of God.”
Yea, for this became the work of the Only Begotten, to unite the divided, and to reconcile the alienated.
Then, lest you should imagine peace in all cases a blessing, He has added,
“Blessed are they which are persecuted for righteousness' sake.”
That is, for virtue's sake, for succor given to others, and for godliness: it being ever His wont to call by the name of “righteousness” the whole practical wisdom of the soul.
“Blessed are you, when men shall revile you and persecute you, and say all manner of evil against you falsely, for my sake. Rejoice, and be exceeding glad.”
As if He said, “Though they should call you sorcerers, deceivers, pestilent persons, or whatever else, blessed are you:” so He speaks. What could be newer than these injunctions? Wherein the very things which all others avoid, these He declares to be desirable; I mean, being poor, mourning, persecution, evil report. But yet He both affirmed this, and convinced not two, nor ten, nor twenty, nor an hundred, nor a thousand men, but the whole world. And hearing things so grievous and galling, so contrary to the accustomed ways of men, the multitudes “were astonished.” So great was the power of Him who spoke.
However, lest you should think that the mere fact of being evil spoken of makes men blessed, He has set two limitations; when it is for His sake, and when the things that are said are false: for without these, he who is evil spoken of, so far from being blessed, is miserable.
Then see the prize again: “Because your reward is great in heaven.” But you, though you hear not of a kingdom given in each one of the blessings, be not discouraged. For although He give different names to the rewards, yet He brings all into His kingdom. Thus, both when He says, “they that mourn shall be comforted;” and, “they that show mercy shall obtain mercy;” and, “the pure in heart shall see God;” and, the peacemakers “shall be called the children of God;” nothing else but the Kingdom does He shadow out by all these sayings. For such as enjoy these, shall surely attain unto that. Think not therefore that this reward is for the poor in spirit only, but for those also who hunger after righteousness, for the meek, and for all the rest without exception.
Since on this account He has set His blessing on them all, that you might not look for anything sensible: for that man cannot be blessed, who is crowned with such things as come to an end with this present life, and hurry by quicker than a shadow.
Source: Homilies on the Gospel of St. Matthew (New Advent)