Matthew 5:3

Christ begins his sermon with blessings, for he came into the world to bless us (Act 3:26), as the great High Priest of our profession; as the blessed Melchizedec; as He in whom all the families of the earth should be blessed, Gen 12:3. He came not only to purchase blessings for us, but to pour out and pronounce blessings on us; and here he does it as one having authority, as one that can command the blessing, even life for evermore, and that is the blessing here again and again promised to the good; his pronouncing them happy makes them so; for those whom he blesses, are blessed indeed. The Old Testament ended with a curse (Mal 4:6), the gospel begins with a blessing; for hereunto are we called, that we should inherit the blessing. Each of the blessings Christ here pronounces has a double intention: 1. To show who they are that are to be accounted truly happy, and what their characters are. 2. What that is wherein true happiness consists, in the promises made to persons of certain characters, the performance of which will make them happy. Now, 1. This is designed to rectify the ruinous mistakes of a blind and carnal world. Blessedness is the thing which men pretend to pursue; Who will make us to see good? Psa 4:6.

— Matthew Henry's Concise Commentary (public domain)

Blessed--Of the two words which our translators render "blessed," the one here used points more to what is inward, and so might be rendered "happy," in a lofty sense; while the other denotes rather what comes to us from without (as Mat 25:34). But the distinction is not always clearly carried out. One Hebrew word expresses both. On these precious Beatitudes, observe that though eight in number, there are here but seven distinct features of character. The eighth one--the "persecuted for righteousness' sake"--denotes merely the possessors of the seven preceding features, on account of which it is that they are persecuted (Ti2 3:12). Accordingly, instead of any distinct promise to this class, we have merely a repetition of the first promise. This has been noticed by several critics, who by the sevenfold character thus set forth have rightly observed that a complete character is meant to be depicted, and by the sevenfold blessedness attached to it, a perfect blessedness is intended. Observe, again, that the language in which these Beatitudes are couched is purposely fetched from the Old Testament, to show that the new kingdom is but the old in a new form; while the characters described are but the varied forms of that spirituality which was the essence of real religion all along, but had well-nigh disappeared under corrupt teaching.

— Jamieson-Fausset-Brown Commentary (public domain)