Here is the oration that the Church prays in the Mass and Office for the feast of Saint Peter Nolasco:
Deus, qui in tuæ caritátis exémplum ad fidélium redemptiónem sanctum Petrum Ecclésiam tuam nova prole fœcundáre divínitus docuísti: ipsíus nobis intercessióne concéde; a peccáti servitúte solútis, in cœlésti pátria perpétua libertáte gaudére.
Here is my translation:
O God, who, for an example of Thy Charity, hast taught Saint Peter Nolasco by heavenly inspiration to make Thy Church fruitful with new offspring for the redemption of the faithful: grant us by his intercession, being released from the servitude of sin, to rejoice in perpetual liberty in the heavenly homeland.
Here is the translation from the Divinum Officium site:
O God, You Who, as an example of Your love, divinely taught St. Peter to enrich Your Church with new offspring, a family of Religious devoted to the ransom of the faithful, grant by his intercession, that we may be released from the slavery of sin and rejoice in lasting freedom in heaven.
In 1218, Saint Peter Nolasco founded the Mercederian Order with the help of the Dominican canonist and Master General, Saint Raymond of Pennafort (also spelled Peñafort) and King Jaime of Aragon. Like the Trinitarians, the Mercederians were mendicant friars whose principle apostolate was the liberation of Christians from captivity to the Muslims, then frequently raiding Europe and making slaves of the baptized.
The reference to God teaching Saint Peter “to make Thy Church fruitful with new offspring for the redemption of the faithful” acknowledges his status as a religious founder, the “offspring” being the numerous friars who, even to this day, see in him a spiritual father.
The reference to being freed from the servitude of sin is a play on the ransoming charism of the Mercedarians (freedom from sin ≈ freedom from Muslim slavery). Similar wordplay is used in the collects for the Mercedarian Frair, Saint Raymond Nonnatus and the Trinitarian founder, Saint Felix of Valois.