Here is the oration that the Church prays in the Mass and Office for Saint Felix of Valois (November 20):
Deus, qui beátum Felícem Confessórem tuum ex erémo ad munus rediméndi captívos cǽlitus vocáre dignátus es: præsta, quǽsumus; ut per grátiam tuam ex peccatórum nostrórum captivitáte, eius intercessióne, liberáti, ad cæléstem pátriam perducámur.
Here is my translation:
O God, who hast deigned by divine inspiration to call blessed Felix Thy Confessor from the desert to the office of redeeming captives: grant, we ask, that by Thy grace and his intersession, being freed from the captivity of our sins, we may be led into the heavenly fatherland.
Here is the translation from the Divinum Officium site:
O God, Who by a sign from heaven didst call thy blessed Confessor Felix out of the desert to become a redeemer of bondsmen, grant, we beseech thee, unto his prayers, that thy grace may deliver us from the bondage of sin, and bring us home unto our very fatherland, which is in heaven.
With Saint John of Matha, Saint Felix (of the Royal House of Valois) was the founder of the Order of the Most Holy Trinity for the Redemption of Captives (O.SS.T.), commonly called the Trinitarians. Aside from being mendicant friars who live the vowed life of the evangelical counsels in common under a rule, their special charism from their inception was the liberation of Christian captives who had been pressed into slavery by the Muslims — the same work undertaken by the Mercederians. Both orders are called “ransoming orders.” Hence the reference in the oration to “redeeming captives.” Just as in the collect for the Mercederian, Saint Raymond Nonnatus, a metaphor is drawn between temporal slavery (to the Muslims) and the spiritual bondage to sin, a theme invoked by Our Lord Himself and by His First Vicar.
The reference to being “called out of the desert” is literal: Saint Felix was a hermit — a word coming from the Latin (borrowed from the Greek) word for desert or wilderness. He was a seventy-year-old priest-hermit when he was called to found this great Order with Saint John of Matha. Saint Felix died roughly fifteen years after the founding of the Order, at the age of eighty-five.
Note that we ask in this prayer to be freed from sin by God’s grace. Let us not overlook such passing doctrinal affirmations in our liturgy. Protestants who accuse Catholics of thinking that we save ourselves by our good works should read how Catholic actually pray. The Church’s rich, anti-Pelagian doctrine of grace is found all over our prayers.