24 Yet, since he was well aware that in matters of this kind the authority of the Roman Pontiff prevails over the opinions of learned men, he took care to call attention to that authority which he recognized as supreme and infallible in settling such questions. To his former disciple, our predecessor of blessed memory Eugene III, he wrote these words which reflect at once his exceeding great love and reverence and that familiarity which becomes the saints: "Parental love knows nothing of lordship, it recognizes not a master but a child even in him who wears the tiara . . . Therefore shall I admonish thee now, not as a master, but as a mother, yea, as a most loving mother."
Source: Doctor Mellifluus (Vatican.va)