‘The Chair of Peter obliges all who hold it to say, as Peter said during a crisis time among the disciples when so many wanted to leave him: “Lord, to whom shall we go? You have the words of eternal life. We have come to believe; we are convinced that you are God's holy one” (Jn 6: 68 ff.).
The One who sits on the Chair of Peter must remember the Lord’s words to Simon Peter at the Last Supper: “...You in turn must strengthen your brothers” (Lk 22: 32). The one who holds the office of the Petrine ministry must be aware that he is a frail and weak human being - just as his own powers are frail and weak - and is constantly in need of purification and conversion.
But he can also be aware that the power to strengthen his brethren in the faith and keep them united in the confession of the Crucified and Risen Christ comes from the Lord. In St Paul’s First Letter to the Corinthians, we find the oldest account we have of the Resurrection. Paul faithfully received it from the witnesses. This account first speaks of Christ's death for our sins, of his burial and of his Resurrection which took place the third day, and then says: “[Christ] was seen by Cephas, then by the Twelve...” (I Cor 15: 4). Thus, the importance of the mandate conferred upon Peter to the end of time is summed up: being a witness of the Risen Christ.
The Bishop of Rome sits upon the Chair to bear witness to Christ. Thus, the Chair is the symbol of the potestas docendi, the power to teach that is an essential part of the mandate of binding and loosing which the Lord conferred on Peter, and after him, on the Twelve’.
From the homily of Pope Benedict XVI
on the occasion of the Mass of Possession of the Chair of the Bishop of Rome
Archbasilica of St John Lateran, 7 May 2005
O most blessed Saviour, who didst vouchsafe thy gracious presence at the Feast of Dedication: be present with us at this time by thy Holy Spirit, and so possess our souls by thy grace; that we may be living temples, holy and acceptable unto thee; who livest and reignest with the Father, in the unity of the Holy Ghost, ever one God, world without end. Amen. - Divine Worship: The Missal.
Fr Lee Kenyon