9 Or, again, since he who plants and he who waters are one, are they not one because, being themselves born again in one baptism they form a ministry of one regenerating baptism? Do not they do the same thing? Are they not one in One? So they who are one through the same thing are one also by nature, not only by will, inasmuch as they themselves have been made the same thing and are ministers of the same thing and the same power.
Source: On the Trinity (New Advent)