Keep us alert, we pray, O Lord our God,
as we await the advent of Christ your Son,
so that when he comes and knocks
he may find us watchful in prayer
and exultant in his praise.
Found as an Advent prayer in 13 medieval manuscripts, including the Gelasian Sacramentary. (Information from Corpus Orationum ed. E. Moeller et al., published in the Corpus Christianorum series.) Not in the 1570 Missal.
The manuscript texts are slightly longer than the one in the 1970 Missal, but the revisers, in removing unnecessary words, retained the structure and sense of the original.
With line 3 compare Cant 5,2 ‘Listen! my beloved is knocking’, Luke 12,36 ‘be like those who are waiting for their master to return from the wedding banquet, so that they may open the door for him as soon as he comes and knocks’, and Apoc 3,20 ‘Listen! I am standing at the door, knocking’.
The official translation nicely replicates in lines 3 and 4 the rhetorical balance of the Latin orationibus vigilantes, et in suis inveniat laudibus exsultantes, and even matches the Latin rhyme on -antes with an alliteration between ‘prayer’ and ‘praise’.
The Prayer over the Offerings and Prayer after Communion for this day are repeated from the Sunday. Altogether, they occur 7 times each in the Missal, always in Advent and always as a pair.