Today's 2nd reading from 1 Cor 12:12-14, 27
Brothers and sisters:
As a body is one though it has many parts,
and all the parts of the body, though many, are one body,
so also Christ.
For in one Spirit we were all baptized into one body,
whether Jews or Greeks, slaves or free persons,
and we were all given to drink of one Spirit.
Now the body is not a single part, but many.
You are Christ’s body, and individually parts of it.
A very good article and daily prayer:
A Catholic Life: Week of Prayer for Christian Unity