- The Sign of the Cross
- Genuflection on Left Knee
- Saying Amen and making the Sign of the Cross after recieving Communion
If you’re talking about these things in the context of the Mass, they come under the GIRM (General Instruction of the Roman Missal) which can be found at
usccb.org/liturgy/current/revmissalisromanien.shtml
For example:
- When the Entrance chant is concluded, the priest stands at the chair and, together with the whole gathering, makes the Sign of the Cross. Then he signifies the presence of the Lord to the community gathered there by means of the Greeting. By this Greeting and the people’s response, the mystery of the Church gathered together is made manifest.
When receiving communion the procedure is:
- If Communion is given only under the species of bread, the priest raises the host slightly and shows it to each, saying, Corpus Christi (The Body of Christ). **The communicant replies, Amen, **and receives the Sacrament either on the tongue or, where this is allowed and if the communicant so chooses, in the hand. As soon as the communicant receives the host, he or she consumes it entirely.
Nothing is said about making the Sign of the Cross after receiving. I would put it in the category of “pious custom.” In other words, if you want to do it go ahead, but there’s no requirement to do it.
As far as genuflecting, the USCCB has an article on the
Real Presence that says this:
The Body and Blood of Christ present under the appearances of bread and wine are treated with the greatest reverence both during and after the celebration of the Eucharist (cf. Mysterium Fidei, nos. 56-61). For example, the tabernacle in which the consecrated bread is reserved is placed “in some part of the church or oratory which is distinguished, conspicuous, beautifully decorated, and suitable for prayer” (Code of Canon Law, Can. 938, §2).
According to the tradition of the Latin Church, one should genuflect in the presence of the tabernacle containing the reserved sacrament. In the Eastern Catholic Churches, the traditional practice is to make the sign of the cross and to bow profoundly. The liturgical gestures from both traditions reflect reverence, respect, and adoration. It is appropriate for the members of the assembly to greet each other in the gathering space of the church (that is, the vestibule or narthex), but it is not appropriate to speak in loud or boisterous tones in the body of the church (that is, the nave) because of the presence of Christ in the tabernacle. Also, the Church requires everyone to fast before receiving the Body and Blood of Christ as a sign of reverence and recollection (unless illness prevents one from doing so). In the Latin Church, one must generally fast for at least one hour; members of Eastern Catholic Churches must follow the practice established by their own Church.
You can see that they’re not citing the Catechism, Canon Law, etc.
