Psalms 138:1

And in the sight of the angels I will sing psalms to you. See the advancement of the penitent, that after confession and repentance he is counted worthy to sing psalms with the angels. But he who sings psalms no longer performs repentance, but gives thanks, and blesses.

I will confess to you, O Lord, with my whole heart. As the wounds are, so too is the poultice. For just as the body has various wounds, so too the soul has its passions and its wounds; and against sin we ought to perform a corresponding repentance. If someone confesses for all his sins, that man confesses to the Lord with his whole heart. For example, someone has committed fornication, and he confesses for the fornication: but since he is either greedy, or wrathful, or a slanderer, or a blasphemer, and has very many vices, that man does not confess with his whole heart. But if someone performs repentance for all the vices and passions of his soul, that man can say: I will confess to you, O Lord, with my whole heart. For you have heard all the words of my mouth. This little verse is not found in the Hebrew. But as for what it says, this is the meaning: Therefore I will confess to you, O Lord, with my whole heart — that is, for all my vices and sins, since I have confessed to you not for one vice alone, and you have heard me.

It is no secret that angels are frequently present, invisibly, at the side of the elect, in order to defend them from the snares of the cunning enemy and uphold them by the great gift of heavenly desire. The apostle attests to this when he says, "Are they not all ministering spirits sent to serve on account of those who receive an inheritance of salvation?" Nevertheless, we should believe that the angelic spirits are especially present to us when we give ourselves in a special way to divine services, that is, when we enter a church and open our ears to sacred reading, or give our attention to psalm singing, or apply ourselves to prayer or celebrate the solemnity of the mass. Hence the apostle advises women to have a veil over their heads in church on account of the angels. And a prophet says, "I will sing psalms to you in the sight of the angels." We are not permitted to doubt that where the mysteries of the Lord's body and blood are being enacted, a gathering of the citizens from on high is present—those who were keeping such careful watch at the tomb where [Christ's] venerable body had been placed and from which he had departed by rising. Hence we must strive meticulously my brothers, when we come into the church to pay the due service of divine praise or to perform the solemnity of the mass, to be always mindful of the angelic presence and to fulfill our heavenly duty with fear and fitting veneration, following the example of the women devoted to God who were afraid when the angels appeared to them at the tomb, and who, we are told, bowed their faces to the earth.