In the Mass of the Last Supper, Pope Francis broke with tradition by washing the feet of both men and women, at least one of them not even Christian. Traditionalists object that the Last Supper was for the apostles, the first bishops, and no women (let alone Muslims) were present. The foot-washing, according to some, must therefore represent an aspect of ordination and should be reserved to men, since the priesthood is for men only and the Last Supper was the beginning of the priesthood. But Francis has given this act a different interpretation.
In fact, he has done so in strict continuity with Pope Benedict, in his book Jesus of Nazareth. There Benedict makes it clear that the foot-washing represents the "descent", the humility, of Christ – his service to all mankind – and not the institution of the priesthood (although on another level the gesture also looks forward to the sacrament of confession that priests will one day offer to the baptized).The priesthood begins not with this act but with the words of institution and the birth of the Church and the Eucharist, when the bread and wine are offered.
The Twelve are not just apostles (priests) but also disciples, and they are disciples before they are priests. Christ descends to the lowest place to serve anyone who will receive him. For Francis, it is clear that Christ came to serve all, to offer salvation to all, even Muslim women. They will not necessarily understand what he does for them now, but one day they will understand (John 13:7). Nothing here is an opening to the ordination of women. Francis is simply giving this gesture its most universal meaning, consistent with the symbolism of Scripture.
Se also "The Mandatum Issue: Beware of Superficial Judgement" by Jeff Mirus.