Why do some some people beat their chests three times when the priest raises the precious body and again when he raises the precious blood?
I don’t know why some people do so at that point in the Mass. Some do it at the three-fold Lamb of God, where God’s mercy is being requested. Others do it at the confiteor, in honor of the old Latin formula of expressing repentance: *“Mea culpa! Mea culpa! Mea maxima culpa!” *(“My fault! My fault! My most grievous fault!”).