Pope Benedict's homily at Mass in St Peter's Basilica this morning is a classic. But not because of it's reference to the authority of the Successor of Peter with regard to excommunication, which is one reference among a range of others.
It offers a commentary on the Scriptural texts of the Liturgy, combining a quite academic knowledge of Scripture and a keen pastoral sense in presenting those texts in the light of that academic knowledge. It is very much in the spirit of the two volumes of Jesus of Nazareth. Particularly striking is the way in which Pope Benedict draws out the Old Testament precedents for the promises to Peter so much associated with this Solemnity, the promise of the "power of the keys" and that the "gates of the underworld will not prevail against" the Church.
And if one does instead just want to focus upon the reference to the power of the keys manifested in the power of imposing or lifting excommunication, then it is also valuable to recall that that same power is also manifested in the generosity of the plenary indulgence granted to those who, near the point of death, receive the Apostolic Blessing or meet the circumstances which allow them to receive the same indulgence in the absence of a priest (cf Enchiridion Indulgentiorum):
12 In articulo mortis 1. Sacerdos, qui christifideli in vitae discrimen adducto sacramenta administrat, eidem benedictionem apostolicam cum adiuncta indulgentia plenaria impertire ne omittat. 2. Quodsi haberi nequit sacerdos, pia Mater Ecclesia eidem christifideli rite disposito benigne indulgentiam plenariam in articulo mortis acquirendam concedit, dummodo ipse durante vita habitualiter aliquas preces fuderit; quo in casu Ecclesia supplet tres condiciones ad indulgentiam plenariam de more requisitas. 3. Laudabiliter ad hanc indulgentiam plenariam acquirendam adhibetur crucifixus vel crux. 4. Eamdem indulgentiam plenariam in articulo mortis christifidelis consequi poterit, etiamsi eodem die aliam indulgentiam plenariam iam acquisiverit. 5. De hac salutari Ecclesiae dispositione in catechesi tradenda fideles opportune et saepe certiores fiant.[Sorry, cannot find an English translation]