So, the last prayer choice under "Close of Worship" in the Additional Prayers and Collects, in the 1937 joint Unitarian and Universalist Hymns of the Spirit is cited in the index as coming from "Liturgy of Malabar, adapted."
Grant, O Lord, that the ears which have heard the voice of thy songs may be closed to the voice of clamor and dispute; that the eyes which have seen thy great love may also behold thy blessed hope; that the tongues which have sung thy praise may speak the truth; that the feet which have walked in thy courts may walk in the region of light; and that the souls of all who here receive thy blessed Spirit may be restored to newness of life. Glory be to thee for thine unspeakable gift. Amen.
I think it's lovely.
Loveliness aside, you may ask, how did a prayer from fifth-century India get into something as New England-bound as the old red hymnal?
My first suspicion is that a Unitarian member of the committee recommended it rather than a Universalist member. I keep finding traces of early twentieth-century interest in antiquarian liturgy among Unitarians: an attempt to find the earliest, most authentic and most lowercase-c catholic strata on which to base liturgical devotion. What keeps this from being simple primitivism is looking past the apostolic age and outside the New Testament. The Liturgy of Malabar is very old, but is the work of a developed church, and one that would have been very foreign to American Protestants. (And provides an link between the Unitarians and their later though brief interest in what we would call the Independent Sacramental Movement. More about that some other time.) Let's put a pin in that curiousity: we will see this interest in a more universal Christian liturgical expression among the Unitarians again, and those influences on the Universalists.
While the prayer appears in different works before the red hymnal and since, its inclusion in W. E. Orchard's The Order of Divine Service for Public Worship is the likely source, as the red hymnal also includes one of his own prayers. (Again, for another time.) This prayer is noted in that index as "(? 5th cent.) Neale and Littledale's Translation." John Mason Neale, better known as a translator of hymns, also translated liturgies. His translation of "O Come, O Come Emmanuel" perhaps his best known.
But their translation of what? The Liturgies of SS. Mark, James, Clement, Chrysostom, and Basil, and the Church of Malabar. Is this Malabar liturgy the original East Syriac rite of the St. Thomas Christians, the restored East Syriac rite of the Eastern Catholics or the adopted West Syriac rite of the indiginizing church? There have been Christians in South India from antiquity, and the traditional founder of these churches was St. Thomas. Today the St. Thomas Christians range in theology and jurisdiction from the Nestorian to Eastern Catholic to Anglican. I ask all this with huge caveats: this is not my field, is centuries old and in languages I don't read. Any clarification from readers would be well appreciated. Neale, in his introduction, isn't clear about the source of the text he translated, but presumably from the Eastern Catholics with noted and obvious changes removed.
So what was the prayer originally? One given by a deacon, at the communion of the faithful. You can read it here.
It's use as a post-communion prayer fits will with a liberal-Reformed use; I'll use it at my next opportunity.