Almighty God,
to whom all hearts are open,
all desires known,
and from whom no secrets are hidden:
cleanse the thoughts of our hearts
by the inspiration of your Holy Spirit,
that we may love you completely,
and rightly magnify your holy name;
through Christ our Lord. Amen.
Source: 11th-century Leofric missal, also attributed to the Gregorian Sacramentary (7th Century)
Source of this version: Modified from 1980 Alternative Service Book via wikipedia.com
Traditional English:
Almighty God, unto whom all hearts be open, all desires known, and from whom no secrets are hid: cleanse the thoughts of our hearts by the inspiration of thy Holy Spirit, that we may perfectly love thee, and worthily magnify thy holy name: through Christ our Lord. Amen.
Source: Book of Common Prayer
Latin:
Deus cui omne cor patet et omnis voluntas loquitur: et quem nullum latet secretum: purifica per infusionem sancti spiritus cogitationes cordis nostri: ut te perfecte diligere et digne laudare mereamur, per dominum nostrum iesum christum filium tuum qui tecum vivit et regnat in unitate eiusdem spiritus sancti deus, per omnia secula seculorum. Amen.
This prayer has its own page on wikipedia.
Variant:
…of your Holy Spirit, that every thought and word of ours may begin from you, and in you be perfectly completed, through Christ our Lord. (The Catholic Prayer Book, 1984, 1986)
Sarum version begins:
O God, unto whom all hearts be open…
A Collection of Prayers 