From a reader:
Why do we bow during the Nicene Creed for the lines “by the power of the holy spirit…” and who started this practice?
These lines are at the heart of the Creed. They are, as it were, the pivot point, of the Creed. In them we express our belief in God’s ineffable communication of His mercy.
“For us men and for our salvation he came down from heaven, and by the Holy Spirit was incarnate of the Virgin Mary, and became man.”
Since at least the 11th century people fell to their knees at this declaration. Dropping, lowering ourselves, or even descending to our knees seems the least we could do at this awesome article of faith about the condescension of God.
In the Novus Ordo at those words people are to bow, instead of kneel. People are to kneel only twice: on 25 March and 25 December. In the Extraordinary Form, people kneel every time the Creed is recited and it is used more often than in the Novus Ordo.
According to Josef Jungmann’s monumental The Mass of the Roman Rite, Peter of Cluny (+1156) wrote that the genuflection at the words et homo factus est was a custom everywhere. Some religious orders such as Premonstratensians and Carthusians had this custom rather early. However, it seems not to have been universal back in the day. It obviously took while to be become uniform. But it did become universal, and it was so for centuries…. until after the Second Vatican Council.