An informed and operative "faith before feeling"

Look upon us, O God, creator and ruler of all things,

and, that we may feel the working of your mercy,

grant that we may serve you with all our heart.

Through. . . .

Respice nos, rerum omnium deus creator et rector,

et, ut tuae propitiationis sentiamus effectum,

toto nos tribue tibi corde servire.

Per. . . .

Sacramentarium Veronense, fol. 132r
(ed. Mohlberg, pp. 161-162).
Bibliotheca Capitularis Veronensis

     Collect for the Twenty-Fourth Sunday in Ordinary Time, Roman missal.

     This is "Leonine" i.e. Veronese sacramentary no. 1045, and, according to Corpus orationum (no. 5110), at least, hadn't appeared in any others since, until re-enlisted for the Missal of 1970.  This means that it was abandoned after the early 7th, 6th, or even 5th century, depending upon when it was actually composed.  In the edition of the "Leonine" ed. Mohlberg, "et" follows rather than precedes "ut":  "Respice nos, rerum omnium deus creator et rector; ut et tuae propitiationis sentiamus effectum, toto nos tribue tibi corde servire:  per" (p. 132, i.e. fol. 107r).

     What's striking to me about this prayer is that it assumes that the Lord must make it possible for us to serve him wholeheartedly if we are going to "feel the operation of [his] propitiation".