Prayer said by the celebrant during the Introductory Rites, after the Salutation, and just before the Summary of the Law is proclaimed by the deacon.
At the Collect for Purity all the altar servers should be standing at their places in the choir stalls.
The Collect for Purity
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.