Augustine of Hippo on Sermon on the Mount

“If any one will piously and soberly consider the sermon which our Lord Jesus Christ spoke on the mount, as we read it in the Gospel according to Matthew, I think that he will find in it, so far as regards the highest morals, a perfect standard of the Christian life: and this we do not rashly venture to promise, but gather it from the very words of the Lord Himself. For the sermon itself is brought to a close in such a way, that it is clear there are in it all the precepts which go to mould the life. … He has sufficiently indicated, as I think, that these sayings which He uttered on the mount so perfectly guide the life of those who may be willing to live according to them, that they may justly be compared to one building upon a rock.”

“What, then, does He say? "Blessed are the poor in spirit, for theirs is the kingdom of heaven." We read in Scripture concerning the striving after temporal things, "All is vanity and presumption of spirit"; but presumption of spirit means audacity and pride: usually also the proud are said to have great spirits; and rightly, inasmuch as the wind also is called spirit. And hence it is written, "Fire, hail, snow, ice, spirit of tempest." But, indeed, who does not know that the proud are spoken of as puffed up, as if swelled out with wind? And hence also that expression of the apostle, "Knowledge puffs up, but charity edifies". And the poor in spirit are rightly understood here, as meaning the humble and God-fearing, i.e. those who have not the spirit which puffs up. Nor ought blessedness to begin at any other point whatever, if indeed it is to attain unto the highest wisdom; "but the fear of the Lord is the beginning of wisdom"; for, on the other hand also, "pride" is entitled "the beginning of all sin." Let the proud, therefore, seek after and love the kingdoms of the earth; but "blessed are the poor in spirit, for theirs is the kingdom of heaven."”