"pardon what conscience dreads and . . . give what prayer does not dare ask" (c. 700 at the very latest)

2010 ICEL:
Almighty ever-living God,
who in the abundance of your kindness
surpass the merits and the desires of those who entreat you,
pour out your mercy upon us
to pardon what conscience dreads
and to give what prayer does not dare to ask.
Through, etc.

Omnipotens sempiterne Deus,
qui abundantia pietatis tuæ
et merita supplicum excedis et vota,
effunde super nos misericordiam tuam,
ut dimittas quæ conscientia metuit,
et adicias quod oratio non præsumit.
Per, etc.

Perisho (in progress):
Almighty, everlasting God,
who, in the abundance of your compassion,
go beyond/overtop both the merits and the desires of suppliants,
pour out upon us your mercy,
that you might break up/disperse/dismiss
     those things that conscience is troubled about
and add to/go beyond what prayer
     does not presume/take for granted/dare.
Through, etc.

     Collect for the Twenty-Seventh Sunday in Ordinary Time, Roman Missal =Gelasian sacramentary no. 1201, and other 8th-century missals (below).  An antecedent of this is no. 917 in the Leonine or Veronese sacramentary (early 7th, but drawing on 5th or 6th century material, at fol. 90v-91r), which the edition of the Leonine ed. Mohlberg reproduces on p. 116 as follows:

Uirtutum caelestium deus, qui plura prestas, quam petimus aut meremur:  tribue, quaesumus, ut tua nobis misericordia conferatur, quod nostrorum non habet fiducia meritorum:  per.

O God of the heavenly virtues, who stand surety for/give [(pr[a]estas)] many more [of them] than we seek or deserve:  grant, in your mercy, we pray, that [that] may be imputed/applied to/conferred upon us which a reliance on our merits does not entail.

Corpus orationum no. 3887 cites Dom G. Morin, “Une collecte romaine du sacramentaire gélasien citée par un écrivain provençal des environs de 494,” Revue bénédictine 30 (1913):  226-228, and G. Morin, “Une restitution en faveur d’Alcuin,” Revue bénédictine 30 (1913):  458-459, in which he almost immediately reverses himself in favor of Alcuin, having been corrected by an article by and a letter from Fr. Henri Brewer.  As this volume of Corpus orationum was published in 1995, I have not looked for any more recent scholarship.
     Missale Francorum (Cod. Vat. Reg. lat. 257), ed. Mohlberg (Rome:  Herder, 1957), no.140 (p. 29) has

Omnipotens sempiterne deus, qui abundantiam pietatis tuae et meritis / supplicum excedis et uota:  effunde super nos misericordiam tuam, ut dimittas quae conscientia metuit, et adicias quod oratio non praesumit:  per dominum

(f. 127v-f. 128r in the manuscript).  Cf. col. 337 of PL 72, which differs less in substituting only adjicias for the critical adicias (rather than "abundantiam . . . meritis" for "abundantia . . . merita" as well).  The ODCC dates  Cod. Vat. Reg. lat 257 to c. 700.
     It also appears on p. 228 of the edition of the Gelasian ed. H. A. Wilson (no. 1201 in the Gelasian sacramentary, and no. 1162 in the supplement to that) where the only difference from the current Missale Romanum appears to fall at the same point (adiicias).  According to the ODCC, the extant manuscripts of the Gelasian sacramentary date from the 8th century.
     "The Sarum missal and previous Prayer Books place it on the Twelfth Sunday after Trinity" (Hatchett, p. 193).  Cf. the Book of common prayer, below.

Father Zuhlsdorf:
Almighty and everlasting God, who in the abundance of Your goodness surpass both the merits and the prayerful vows of suppliants, pour forth Your mercy upon us, so that You set aside those things which our conscience fears, and apply what our prayer dares not.

1976 Book of common prayer, Proper 22, Contemporary:
Almighty and everlasting God, you are always more ready to hear than we to pray, and to give more than we either desire or deserve:  Pour upon us the abundance of your mercy, forgiving us those things of which our conscience is afraid, and giving us those good things for which we are not worthy to ask, except through the merits and mediation of Jesus Christ our Saviour; who, etc.

1976 Book of common prayer, Proper 22, Traditional =1928 Book of common prayer, Twelfth Sunday after Trinity (except for the punctuation):
Almighty and everlasting God, who art always more ready to hear than we to pray, and art wont to give more than either we desire or deserve:  Pour down upon us the abundance of thy mercy, forgiving us those things whereof our conscience is afraid, and giving us those good things which we are not worthy to ask, but through the merits and mediation of Jesus Christ thy Son our Lord; who, etc.

1549 Booke of the common prayer, Twelfth Sunday after Trinity:
Almightie and euerlastyng God, which art alwayes more ready to heare then we to praye, and art wont to geue more than eyther we desyre or deserue; Powre downe upon us the aboundance of thy mercy; forgeuing us those thynges wherof our conscience is afrayde, and geuying unto us that that our prayer dare not presume to aske, thrugh Jesus Christe our Lorde.

Sarum missal, Twelfth Sunday after Trinity:
Omnipotens sempiterne Deus, qui abundantia pietatis tuæ et merita supplicum excedis et vota, effunde super nos misericordiam tuam, ut dimittas quæ conscientia metuit, et adjicias quod oratio non præsumit.  Per Dominum.

1973 ICEL (yikes!):
Father, your love for us surpasses all our hopes and desires. Forgive our failings, keep us in your peace and lead us in the way of salvation.