Sign of the Cross during Penetential Rite

[Duc_In_Altum]

At most of the Masses I have been to, the faithful make the Sign of the Cross at the words concluding the Penetential Rite, "May Almighty God have mercy on us, forgive us our sins, and bring us to everlasting life." Why do we do this? What is its origin? Why do some parishes not do this?

Thank You and God Bless.

-Joe

[cappie]

The General Instruction says:

The Act of Penitence
51. Then the priest invites those present to take part in the Act of Penitence, which, after a brief pause for silence, the entire community carries out through a formula of general confession. The rite concludes with the priest’s absolution, which, however, lacks the efficacy of the Sacrament of Penance.

The fact that some people make this sign of the cross is mistaken for in the "old" Mass the sign of the cross was incorporated in the prayer:

[i]Indulgentiam, + absolutionem, et remissionem peccatorum nostrorum tribuat nobis omnipotens et misericors Dominus. Amen[/i]

This prayer followed the prayer:

[i]Misereatur tui omnipotens Deus, et, dimissis peccatis tuis, perducat te ad vitam aeternam. Amen
[/i]
This prayer did not contain a sign of the cross and now is the only prayer that concluded the penitential rite