The Vatican's St. Martha Dispensary was founded in 1922 and, staffed by volunteers, it provides medical care and basic necessities to any child in need; most of the clients are immigrants.

Dozens of children, their parents and the clinic volunteers anticipated Pope Francis' 82nd birthday, singing for him and giving him a large cake Dec. 16. His birthday was the next day.

"I wish you all a merry Christmas, a good holy Christmas, and I thank you from the bottom of my heart for all that you do. Really," the Pope said. "And, I also hope that no one gets indigestion from a cake that big. Thank you!"

In brief comments to the women religious who run the clinic and to the doctors and others who volunteer there, Pope Francis said, "Working with children isn't easy, but they teach us much."

"They taught me something: to understand the reality of life, you must lower yourself, like you bend down to kiss a child. They teach us this," he said. "The proud and haughty cannot understand life because they are not capable of lowering themselves."

Everyone who works at the clinic gives children something, the Pope said. "But they give us this proclamation, this teaching: bow down, be humble and you will learn to understand life and understand people."