When it is said
In the old Roman Mass book a priest said it as the last prayer of a Mass for sins. The same book also sets it among the prayers for forgiveness.
In 1864 the Oxford scholar William Bright listed it among the English Prayer Book’s prayers for private or family prayer, under “For Pardon”.
At home someone might say it for themselves, or for a person they love who cannot break free.
Where it comes from
No author known
Where does it come from?
The prayer stands among the prayers for forgiveness in the Gregorian Sacramentary, the Roman Church’s book of Mass prayers. Charlemagne asked Pope Hadrian I for this book, and the Pope sent it from Rome with a letter dated between AD 784 and 791. The words about the chain are almost the same in an older Roman book, the Gelasian Sacramentary.
The Gregorian Sacramentary, ed. H. A. Wilson (1915), introduction and page 123; William Bright, Ancient Collects (1864), appendix
How did it reach English?
In England the prayer closed the old Latin litany, and it was kept in the English Litany of 1544. It fell out of use under King Edward VI and came back in the Prayer Book of 1559. The Book of Common Prayer of 1662 gives it as a prayer to say after any of its prayers for special needs.
William Bright, Ancient Collects (1864), appendix; The Book of Common Prayer (1662), Prayers and Thanksgivings
In Latin
Deus, cui proprium est misereri semper et parcere,
suscipe deprecationem nostram,
et quos delictorum catena constringit,
miseratio tuae pietatis absolvat. Per.
From the Gregorian Sacramentary, ed. H. A. Wilson (London, 1915), page 123, on archive.org.