Question: What procedure was being performed while he gave his reasoning ?
Sentence: Beginning with St. Gregory Nazianzen, his explanation of the "purification" of Jesus and Mary at the circumcision (Luke 2:22) prompted him to consider the primary meaning of "purification" in Christology (and by extension in Mariology) to refer to a perfectly sinless nature that manifested itself in glory in a moment of grace (e.g., Jesus at his Baptism).
Answer in sentence: yes