Keep, we beseech thee, O Lord, thy Church with thy perpetual mercy: and, because the frailty of man without thee cannot but fall; keep us ever by thy help from all things hurtful, and lead us to all things profitable to our salvation; through Jesus Christ thy Son our Lord, who liveth and reigneth with thee, in the unity of the Holy Ghost, ever one God, world without end. Amen. - Collect for the Fifteenth Sunday after Trinity, Divine Worship: The Missal.
‘The Collect is ancient and, with the [Prayer Book] Epistle and Gospel, is the same as used before the Reformation, though both Epistle and Gospel are lengthened. It is interesting to notice how constantly the frailty of our nature is insisted on in the Collects.
In this Collect as elsewhere in the Prayer Book we call ourselves God’s Church. Keep us, thy Church, with thy perpetual mercy! We need God's protection because of our frailty or fragility; our good resolutions are so apt to be broken. So we ask to be kept from hurtful things to be given things profitable to our salvation.
...The Collect does not tell us the names of the things we need, but it says plainly that we need God’s help to keep us from things hurtful. God’s help comes to us through prayer and sacrament, through conscience guiding us, through God's holy inspiration, through the gifts of the Spirit, and they will lead us to things profitable to our salvation.
Just as we need to be careful about little things if we are to be profitable, in things spiritual we must be equally careful if they are to be profitable to our salvation. We need above all things the gift of holy fear... [w]e should be afraid to think or say or do anything which would injure God’s Holy Name, or his Word or his Church. If we have this sort of fear it will lead us to things profitable to our salvation’.
from Teaching the Collects, 1965, by H.E. Sheen
Fr Lee Kenyon