The Salt Of The Earth

Vos estis sal terrae... Causa est quare in tribulatione deficere non debetis, quasi diceret: Necesse est, ut tribulationes constanter patiamini, quia vos estis sal terrae, hoc est fortitudo terrenorum, et ideo defectus vester esset defectus aliorum. Nota quod ipsi vocantur sal et lux mundi. Duo enim sunt necessaria fidelibus: illuminatio mentis, et fortitudo operationis. Sunt quidem apostoli lux, per quos alii illuminantur, et a tenebris ignorantiae purgantur, et dicuntur sal quasi salus, qua iidem servantur a corruptione mentis et corporis. Sicut enim sal carnem a corruptione servat, et vermes ibi exstinguit, et fluidos humores siccat, sic et apostoli, postquam aliquos illuminaverint, eos in bono proposito debent servare, et vermes vitiorum exstinguere, et omnem exsiccare carnalitatem. Unde in Psalmo:  Dominus illuminatio mea, et salus. Si enim aliquis Deum cognoscit, et firmitatem propositi non habeat, non prodest: et alibi dicitur per prophetam: Posui te in lucem gentium, ut sis salus mea usque in extremum terrae. Sal quidem facit sterilem terram, quae enim salsa est, sterilis est. Propterea destructis urbibus, victores supra fundamenta arabant, et sal supra seminabant, ut significarent sterilitatem et vastationem. Propterea dicuntur apostoli sal, quia praedicatio eorum est condimentum aliorum. Nulla enim praedicatio valet, nisi condimento apostolicae doctrinae sit suffulta. Quod si sal evanuerit, id est fortitudo vestra defecerit in tribulatione, in quo salietur? id est in quibus populus infirmior confirmabitur? Ad nihilum valet.  Anselmus Laudunensis, Enarrationes In Matthaeum, Caput V Source: Migne PL 162.1290d-1291c

You are the salt of the earth... 1 Which is the reason why you should not fall in tribulation, as if He said, 'It is necessary that you continually suffer tribulations because you are the salt of the earth, that is, the strength of the earth, and therefore your failure shall be the failure of others.' Note that that they are called both salt and light, for these two are both needful for the faithful, the illumination of the mind and strength in works. They are certainly Apostles who are light, through whom others are enlightened and purged of their darkness of ignorance, and they are called salt as preservers, by which the body and mind is protected from corruption. As salt protects meat from rotting, killing worms there and drying up fluids, so even the Apostles, after they have illuminated others should guard them in their good resolution, killing off the worms of the vices and drying up all carnality. Whence the Psalm says, 'Lord, my illumination and my salvation.' 2 If someone knows God and has no firmness of will, it cannot profit him, as elsewhere it is said through the prophet, 'I have placed you as a light for the peoples, that you may be my salvation even to the ends of the earth.' 3 Salt does make earth sterile, for when it has been salted it is sterile, and because of this when cities are destroyed the victors plough the foundations and seed it with salt to signify its sterility and ruin, but the Apostles are said to salt because their preaching is the flavouring of others. For no preaching avails unless it is suffused with the flavouring of the Apostolic teaching. If the salt is tasteless, if your strength fails in trials, of what use is it? That is, how will a weak people be strengthened? 'It is of no benefit at all.'  Anselm of Laon, Commentary On The Gospel of Saint Matthew, Chapter 5 1 Mt 5.13 2 Ps 26.1 3 Isaiah 49.6