"There is one other point which I would like to emphasize, since it significantly affects the authenticity of our communal sharing in the Eucharist. It is the impulse which the Eucharist gives to the community for a practical commitment to building a more just and fraternal society. In the Eucharist our God has shown love in the extreme, overturning all those criteria of power which too often govern human relations and radically affirming the criterion of service: 'If anyone would be first, he must be last of all and servant of all' (Mark 9:35). It is not by chance that the Gospel of John contains no account of the institution of the Eucharist, but instead relates the 'washing of feet' (cf. John 13:1-20): by bending down to wash the feet of his disciples, Jesus explains the meaning of the Eucharist unequivocally. Saint Paul vigorously reaffirms the impropriety of a Eucharistic celebration lacking charity expressed by practical sharing with the poor (cf.1 Cor 11:17-22, 27-34)."
John Paul II, Apostolic Letter Mane Nobiscum Domine, 28