The Symbol or Creed is sung or recited by the Priest together with the people (cf. no. 68) with everyone standing. At the words et incarnatus est, etc. (and by the Holy Spirit . . . and became man) all make a profound bow; but on the Solemnities of the Annunciation and of the Nativity of the Lord, all genuflect.
Genu = knee, flectere = to bend. This is probably easier to remember when the creed is chanted and this part is extended (timewise), as this (genuflecting) was/has been the traditional posture after “Descendit de coelis” (descended from heaven) through “Et Homo Factus Est” (and He was made Man). I’ve seen where the bow is made in addition to the genuflection at those last few words.
Historically, this was done at the reading of the Martyrology for that day, after Prime on Christmas Eve. At the abbey I’m associated with it’s done after Lauds on Christmas Eve as they no longer recite Prime.
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