Today, there was a visiting priest celebrating Mass and our parish priest was there too. Except, our parish priest did not participate in celebrating the Mass, rather he took place as if he were an altar server. With the exception that he preached the homily (at which time he wore a stole, at all other times he had taken it off). Neither did he receive holy communion. But he did distribute the Precious Blood? (He wore his stole at this point as well.) I’m not sure the reasoning behind all of this. The only thing I can think of is that he had already celebrated Mass early in the morning at our missionary parish.
Is it possible that your parish priest had a mass earlier or later in the day, like a funeral or another daily mass? Priests are only allowed to take one stipend per day, yet are permitted to celebrate 2 masses per day if there is a pastoral need. This is in accord with Canon Law. When a visiting priest drops by and would like to say mass, he would be the beneficiary of the second stipend and the Parish Priest could still participate by proclaiming the gospel, preaching and helping with the distribution of Holy Communion. It really should be a concelebration situation for the Parish Priest, rather than a stole on, then off, MC type of a role.
Here are some answers from the GIRM about priests, masses, frequencies and recommendations.
A priest should not ordinarily sit in the pews like/as if a layperson because by doing so, he is not exercising the role that is consistent with his state in life. [The Mass] It is therefore of the greatest importance that the celebration of the Mass—that is, the Lord’s Supper—be so arranged that the sacred ministers and the faithful taking part in it, according to the proper state of each, may derive from it more abundantly, those fruits for the sake of which Christ the Lord instituted the Eucharistic Sacrifice of his Body and Blood and
entrusted it to the Church, his beloved Bride, as the memorial of his Passion and Resurrection.
Concelebration, which appropriately expresses the unity of the priesthood, of the Sacrifice, and also of the whole People of God, is prescribed by the rite itself for the Ordination
of a Bishop and of priests, at the blessing of an abbot, and at the Chrism Mass. Unless the good of the Christian faithful requires or suggests otherwise, concelebration is also recommended at
a. The Evening Mass of the Lord’s Supper;
b. The Mass during Councils, meetings of Bishops, and synods;
c. The conventual Mass and the principal Mass in churches and oratories; (religious orders)
d. Masses at any kind of meeting of priests, either secular or religious.
An individual priest is, however, permitted to celebrate the Eucharist individually, though not at the same time as a concelebration is taking place in the same church or oratory. On Holy Thursday, however, and for Mass of the Easter Vigil, it is not permitted to celebrate individually.
Visiting priests should be gladly welcomed to eucharistic concelebration, as long as their priestly standing is ascertained.
Where there is a large number of priests, concelebration may take place even several times on the same day, wherever necessity or pastoral benefit suggest it. Nevertheless, it must be held at different times or in distinct sacred places.
Lastly, It is for the Bishop, in accordance with the norm of law, to regulate the discipline for concelebration in all churches and oratories of his diocese.
A priest on Vacation should make the necessary arrangements to celebrate mass privately or at a nearby parish or may concelebrate at a regularly scheduled mass if he makes the appropriate arrangements.
The Eucharistic Celebration always retains its efficacy and dignity because it is the action of Christ and the Church, in which the priest fulfills his own principal office and always acts for the people’s salvation. It is therefore recommended that the priest celebrate the Eucharistic Sacrifice even daily, if possible