Building And Guarding

Haec cantica, ut saepe diximus, ascendentium sunt. Qualiter ascendentium? Scilicet amando Deum. Qui Deum amat, ascendit; qui saeculum amat, cadit. Sed hujus psalmi titulo additum est: Canticum Graduum Salomonis. Videamus, cur nomen Salomonis in hoc tantummodo [loco] additum sit. Salomon interpretatur pacificus. Quis [est] iste pacificus, nisi verus Salomon Dominus noster Jesus Christus, qui coelestia et terrestria pacificavit in sanguine suo, et fecit utraque unum, duos sibi parietes conjungens in seipso, summo angulari lapide. Nam Ecclesia de duobus populis, id est, circumcisionis et praeputii copulavit in unum ovile, ut sit unus pastor et unum ovile. De isto vero Salomone in capite hujus psalmi dicitur: Nisi Dominus aedificaverit domum, in vanum laborant, qui aedificant eam. Nisi Dominus aedificet Ecclesiam absque macula et ruga, in vanum laborat omnis praedicator. Qui sunt qui in vanum laborant, nisi haeretici qui laborant Ecclesiam congregare, sed absque Domino; ideo vanum est opus illorum. Ex quo populus fidelis aedificatus est, custos est ipsius Dominus noster Jesus Christus, qui aedificat, qui conservat, qui protegit, qui remunerat; ille solus in omnibus et aedificator et custos. Ideo dixit in sequenti versu: Nisi Dominus custodierit civitatem, frustra vigilat qui custodit eam. Ista est civitas, de qua saepius in his Graduum psalmis cantatur, spiritalis utique Jerusalem. Alcuinus, Expositio in Psalmos Graduales, Psalmus CXXVI Source: Migne PL 100.628b-d

These songs, as we have often said, are songs of ascent. In what way are they ascents? By loving God. He who loves God, he ascends, and he who loves the world, he falls. But to the title of this Psalm has been added, 'A song of ascent, by Solomon.' Let us see why the name of Solomon has been added in this place only. Solomon is translated as peaceful. Who is this peace but the true Solomon our Lord Jesus Christ, who pacified heaven and earth with His own blood, and made two one, joining the two parts in Himself, He who is the best cornerstone. For the Church is from two peoples, that is, He binds into one flock the people of the circumcision and the uncircumcision, so that there may be one shepherd and one flock. At the beginning of this Psalm it is said of this true Solomon, Unless the Lord shall build the house, they labour in vain who build it. 1 Unless the Lord builds the Church without spot or wrinkle, every preacher labours in vain. Who are those who labour in vain but the heretics who toil to gather their church, but without the Lord, and therefore their work is in vain. It has been built up from a faithful people, and its guardian is our Lord Jesus Christ, He who builds, He who preserves, He who protects, and He who rewards. He alone among everyone is the builder and guardian. Therefore it is said in the following line, 'Unless the Lord guards the city, they who watch guard it in vain.' This is the city which is often sung about in the Psalms of ascent, which is the spiritual Jerusalem. Alcuin of York, Commentary on the Gradual Psalms, from Psalm 126 1 Ps 126.1 2 Mt 7.24-27 3 Isaiah 2.2