This text comes from The Complete Poetical Works of John Greenleaf Whittier, a historical songbook transcribed on Wikisource and reproduced from the pinned revision linked below.
A tale for Roman guides to tell
To careless, sight-worn travellers still,
Who pause beside the narrow cell
Of Gregory on the Cælian Hill.
One day before the monk's door came
A beggar, stretching empty palms,
Fainting and fast-sick, in the name
Of the Most Holy asking alms.
And the monk answered, "All I have
In this poor cell of mine I give,
The silver cup my mother gave;
In Christ's name take thou it, and live."
Years passed; and, called at last to bear
The pastoral crook and keys of Rome,
The poor monk, in Saint Peter's chair,
Sat the crowned lord of Christendom.
"Prepare a feast," Saint Gregory cried,
"And let twelve beggars sit thereat."
The beggars came, and one beside,
An unknown stranger, with them sat.
"I asked thee not," the Pontiff spake,
"O stranger; but if need be thine,
I bid thee welcome, for the sake
Of Him who is thy Lord and mine."
A grave, calm face the stranger raised,
Like His who on Gennesaret trod,
Or His on whom the Chaldeans gazed,
Whose form was as the Son of God.
"Know'st thou," he said, "thy gift of old?"
And in the hand he lifted up
The Pontiff marvelled to behold
Once more his mother's silver cup.