From Dom Guéranger's The Liturgical Year.
We were celebrating, not many days ago, the memory of Peter Nolasco, who was inspired, by the holy Mother of God, to found an Order for the ransoming of Christian captives from the infidels: to-day, we have to honour the generous saint, to whom this sublime work was first revealed. He established, under the name of the most holy Trinity, a body of religious men, who bound themselves by vow to devote their energies, their privations, their liberty, nay, their very life, to the service of the poor slaves who were groaning under the Saracen yoke. The Order of the Trinitarians, and the Order of Mercy, though distinct, have the same end in view, and the result of their labours, during the six hundred years of their existence, has been the restoration to liberty and preservation from apostasy of upwards of a million slaves. John of Matha, assisted by his faithful co-operator, Felix of Valois (whose feast we shall keep at the close of the year), established the centre of his grand work at Meaux, in France. We are preparing for Lent, when one of our great duties will have to be that of charity towards our suffering brethren: what finer model could we have than John of Matha, and his whole Order, which was called into existence for no other object than that of delivering from the horrors of slavery brethren who were utter strangers to their deliverers, but were in suffering and in bondage. Can we imagine any almsgiving, let it be ever so generous, which can bear comparison with this devotedness of men, who bind themselves by their rule, not only to traverse every Christian land begging alms for the ransom of slaves, but to change places with the poor captives, if their liberty cannot be otherwise obtained? Is it not, as far as human weakness permits, following to the very letter the example of the Son of God Himself, who came down from heaven that He might be our ransom and our Redeemer? We repeat it: with such models as these before us, we shall feel ourselves urged to follow the injunction we are shortly to receive from the Church, of exercising works of mercy towards our fellow-creatures, as being one of the essential elements of our lenten penance.
But it is time we should listen to the account given us by the liturgy of the virtues of this apostolic man, who has endeared himself, both to the Church and to mankind, by his heroism of charity.
Joannes de Matha, Ordinis sanctissimæ Trinitatis redemptionis captivorum institutor, Falcone in Provincia natus est, parentibus pietate et nobilitate conspicuis. Studiorum causa Aquas Sextias, mox Parisios profectus, confectoque theologiæ curriculo, magisterii lauream adeptus, doctrinæ, et virtutum splendore enituit: quibus motus Parisiensia Antistes, ad sacrum presbyteratus ordinem, præ humilitate reluctantem promovit, eo consilio, ut in ea civitate commorans, sapientia et moribus studiosæ juventuti præluceret. Cum autem in sacello ejusdem episcopi, ipso cum aliis adstante, primum Deo sacrum offerret, cœlesti favore meruit recreari. Nam angelus candida et fulgenti veste indutus, cui in pectore crux rubei et cærulei coloris assuta erat, brachiis cancellatis, et super duos captivos ad latera pósitos, Christianum unum, alterum Maurum, extensis apparuit. Qua visione in exstasim raptus, intellexit protinus vir Dei se ad redimendos ab infidelibus captivos destinari.
Quo vero maturius in re tanti momenti procederet, in solitudinem secessit; ibique divino nutu factum est, ut Felicem Valesium in ipsa eremo jam multis annis degentem repererit. Cum quo inita societate, se per triennium in oratione et contemplatione, omniumque virtutum studio exercuit. Contigit autem, ut dum secum de rebus divinis prope fontem colloquerentur, cervus ad eos accesserit, crucem inter cornua gerens, rubei et cærulei coloris. Cumque Felix ob rei novitatem miraretur, narravit ei Joannes visionem in prima Missa habitam: et exinde ferventius orationi incumbentes, ter in somnis admoniti, Romam proficisei decreverunt, ut a summo Pontifice novi Ordinis pro redimendis captivis institutionem impetrarent. Electus fuerat eo tempore Innocentius tertius; qui, illis benigne acceptis, dum secum de re proposita deliberaret, in festo sanctæ Agnetis secundo, Laterani intra Missarum solemnia, ad sacræ Hostiæ elevationem, angelus ei candida veste, cruce bicolori, specie redimentis captivos apparuit. Quo viso, Pontifex institutum approbavit, et novum Ordinem sanctissimæ Trinitatis redemptionis captivorum vocari jussit, ejusque professoribus albas vestes, cum cruce rubei et cærulei coloris præbuit.
Sic stabilito Ordine, sancii fundatores in Galliam redierunt; primoque cœnobio Cervi Frigidi in diœcesi Meldensi constructo, ad ejus regimen Felix remansit, et Joannes Romam cum aliquot sociis reversus est ubi Innocentius domum, ecclesiam, et hospitale sancti Thomæ de Formis in monte Cœlio eis donavit, cum multis redditibus, et possessionibus. Datis quoque litteris ad Miramolinnm regem Marochii, opus redemptionis felici auspicio inchoatum fuit. Tum ad Hispanias, sub jugo Saracenorum, magna ex parte oppressas, Joannes profectus est, regumque, principum, atque aliorum fidelium animos ad captivorum et pauperum commiserationem commovit. Monasteria ædificavit, hospitalia erexit, magnoque lucro animarum, plures captivos redemit. Romam tandem reversus, sanctisque operibus incumbens, assiduis laboribus attritus, et morbo confectus, ardentissimo Dei et proximi amore exæstuans, ad extremum devenit. Quare fratribus convocatis, eisque ad opus redemptionis cœlitus præmonstratum efficaciter cohortatis, obdormivit in Domino, sextodecimo kalendas Januarii, anno salutis millesimo ducentesimo decimo tertio, ejusque corpus in ipsa ecclesia Sancti Thomæ de Formis condigno honore tumulatimi fuit.
John of Matha, the institutor of the Order of the most Holy Trinity for the ransom of captives, was born at Faucon, in Provence, of parents conspicuous for their nobility and virtue. He went through his studies first at Aix, and afterwards at Paris, where, after having completed his theological course, he received the degree of doctor. His eminent learning and virtues induced the bishop of Paris to promote him, in spite of his humble resistance, to the holy order of priesthood, that, during his sojourn in that city, he might be a bright example to young students by his talents and piety. While celebrating his first Mass in the bishop’s chapel, in the presence of the prelate and several assistants, he was honoured by a signal favour from heaven. There appeared to him an angel clad in a white and brilliant robe; he had on his breast a red and blue cross, and his arms were stretched out, crossed one above the other, over two captives, one a Christian, the other a Moor. Falling into an ecstasy at this sight, the man of God at once understood that he was called to ransom captives from the infidels.
But, that he might the more prudently carry out so important an undertaking, he withdrew into a solitude. There by divine appointment, he met with Felix of Valois, who had been living many years in that same desert. They agreed to live together, and for three years did John devote himself to prayer and contemplation, and the practice of every virtue. It happened, that as they were one day seated near a fountain, conferring with each other on holy things, a stag came towards them, bearing a red and blue cross between his antlers. John, perceiving that Felix was surprised by so strange an occurrence, told him of the vision he had had in his first Mass. They gave themselves more fervently than ever to prayer, and having been thrice admonished in sleep, they resolved to set out for Rome, there to obtain permission from the sovereign Pontiff to found an Order for the ransom of captives. Innocent III., who had shortly before been elected Pope, received them kindly, and while deliberating upon what they proposed, it happened that as he was celebrating Mass in the Lateran church, on the second feast of St. Agnes, there appeared to him, during the elevation of the sacred Host, an angel robed in white, bearing a two-coloured cross, and in the attitude of one that was rescuing captives. Whereupon, the Pontiff gave his approbation to the new institute, and would have it called the Order of the most Holy Trinity for the ransom of captives, bidding its members wear a white habit, with a red and blue cross.
The Order being thus established, its holy founders returned to France, and erected their first monastery at Cerfroid, in the diocese of Meaux. Felix was left to govern it, and John returned, accompanied by a few of his brethren, to Rome. Innocent III. gave them the house, church, and hospital of St. Thomas de Formis, together with various revenues and possessions. He also gave them letters to Miramolin, king of Morocco, and thus was prosperously begun the work of ransom. John afterwards went into Spain, a great portion of which country was then under the Saracen yoke. He stirred up kings, princes, and others of the faithful, to compassion for the captives and the poor. He built monasteries, founded hospitals, and saved the souls of many captives by purchasing their freedom. Having, at length, returned to Rome, he spent his days in doing good. Worn out by incessant labour and sickness, and burning with a most ardent love of God and his neighbour, it was evident that his death was at hand. Wherefore, calling his brethren round him, he eloquently besought them to labour in the work of ransom, which heaven had entrusted to them, and then slept in the Lord, on the sixteenth of the Calends of January (December 17), in the year of grace 1213. His body was buried with the honour that was due to him in the same church of St. Thomas de Formis.
And now, generous-hearted saint, enjoy the fruits of thy devoted charity. Our blessed Redeemer recognizes thee as one of His most faithful imitators, and the whole court of heaven is witness of the recompense wherewith He loves to honour thy likeness to Himself. We must imitate thee; we must walk in thy footsteps; for we too hope to reach the same eternal resting-place. Fraternal charity will lead us to heaven, for the works it inspires us to do have the power of freeing the soul from sin, as our Lord assures us. Thy charity was formed on the model of that which is in the heart of God, who loves our soul yet disdains not to provide for the wants of our body. Seeing so many souls in danger of apostasy, thou didst run to their aid, and men were taught to love a religion which can produce heroes of charity like thee. Thy heart bled at hearing of the bodily sufferings of these captives, and thy hand broke the chains of their galling slavery. Teach us the secret of ardent charity. Is it possible that we can see a soul in danger of being lost, and remain indifferent? Have we forgotten the divine promise, told us by the apostle: ‘He that causeth a sinner to be converted from the error of his way, shall save his soul from death, and shall cover a multitude of his own sins’? Obtain for us, also, a tender compassion for such as are in bodily suffering and poverty, that so we may be generous in comforting them under these trials, which are but too often an occasion of their blaspheming Providence. Dear friend and liberator of slaves! pray, during this holy season, for those who groan under the captivity of sin and Satan; for those, especially, who, taken with the frenzy of earthly pleasures, feel not the weight of their chains, but sleep on peacefully through their slavery. Ransom them by thy prayers, convert them to the Lord their God, lead them back to the land of freedom. Pray for France which was thy country, and save her from infidelity. Protect the venerable remnants of thy Order, that so it may labour for the present wants of the Christian world, since the object for which thou didst institute it has ceased to require its devotedness.
 Ecclus. iii. 33.
 St. James v. 20.