Concelebration

[MissyP89]

If a priest is present at a Mass, is he required to be a concelebrant?

I've never seen a priest simply attend Mass, and I feel like they would appreciate just being in the pews from time to time.

[cappie]

Under the old code a priest was obliged to say Mass only several times a year, although bishops and superiors were to see that they celebrated at least every Sunday and holy day of obligation. The present canon does not lay down a minimum it encourages daily celebration, as did Vat II precisely because in celebrating Mass a priest is fulfilling his principal function.

Can. 904 Remembering always that in the mystery of the Eucharistic Sacrifice the work of redemption is continually being carried out, priests are to celebrate frequently. Indeed, daily celebration is earnestly recommended, because, even if it should not be possible to have the faithful present, it is an action of Christ and of the Church in which priests fulfil their principal role..

Can. 905 §1 Apart from those cases in which the law allows him to celebrate or concelebrate the Eucharist a number of times on the same day, a priest may not celebrate more than once a day.

§2 If there is a scarcity of priests, the local Ordinary may for a good reason allow priests to celebrate twice in one day or even, if pastoral need requires it, three times on Sundays or holydays of obligation.

So while the priest is encouraged to celebrate daily there is no absolute need for him to do so or to concelebrate except for the reason cited above that is he fulfills his principal role as a priest.