Adesto, Domine, supplicibus tuis,
et spem suam in tua misericordia collocantes
ut, a peccatorum labe mundati,
in sancta conversatione permaneant,
et promissionis tuae perficiantur haeredes.
This prayer was not in a pre-Conciliar edition of the Missale Romanum, but a prayer from the Veronese Sacramentary in the month of September, a fast time, it was altered by The Redactors, for the Novus Ordo. The Veronese has et consequentes sufficientiam temporalem promissionis tuae perficiantur heredes.
Tueor is one of those verbs with a zillion possibilities. The outstanding Lewis & Short indicates that it means, in the first place, "to see, to look or gaze upon, to watch, view" and hence it shifts in meaning to "to see or look to, to defend, protect".
Permaneo, which is basically, "to stay to the end; to hold out, last, continue, endure, remain; to persist, persevere" is also, interestingly, "to abide in a way, rule, or mode of life, to live by, to devote one’s life to" as is attested to in the Vulgate.
Conversatio we have seen in an earlier Lenten entry.
Be present, O Lord, to Your humble petitioners,
and graciously protect those placing their hope in Your mercy,
so that, cleansed from the stain of sins,
they may persevere to the end in holy manner of living
and as the heirs of Your promise be brought to perfection.
Even in a bare bones metaphrase such as this, the power of the Latin prayer shows forth.
Perseverance it is key to this prayer. We all have something given to us by god to accomplish in life. We require both grace and elbow grease to persevere in our vocations. The Church herself has a mission to fulfill and she also must be faithful to her Spouse, Christ the Lord. The integrity of our vocations must be defended as well. The Church, from time to time, must make firm, clear and bold statements of belief and also exercise internal discipline for the sake of fulfilling her God given vocation. At times she must defend the flock from error and disorder.
You might remember that in 1998 the late Pope John Paul II issued a Motu proprio document called Ad tuendam fidem. By this instrument, the Church’s legislator inserted some canons into the Code of Canon Law for both the Latin and Eastern Churches. The laws aimed to defend the Faith from theological errors especially by those who teach.
We need clear doctrine, clear prayers, and clear willingness to adhere to them on the part of her duly appointed pastors. Hopefully the ongoing project of preparing a new translation of the Missale Romanum will be a contribution, not an obstacle.
Also, I note with interest the theme of adoption/sonship/inheritance. If I am not mistaken, we will see this taken up again.