What Francis did on the birthday of our Lord Jesus Christ near the little town called Greccio in the third year before his glorious death should be especially noted and recalled with reverent memory. In that place there was a certain man named John, of good reputation and an even better life, whom blessed Francis loved with a special love, for in the place where he lived he held a noble and honorable position in as much as he had trampled upon the nobility of his birth and pursued nobility of soul. Blessed Francis sent for this man, as he often did, about fifteen days before the birth of the Lord, and he said to him: "If you want us to celebrate the present feast of our Lord at Greccio, go with haste and diligently prepare what I tell you. For I wish to do something that will recall to memory the little Child who was born in Bethlehem and set before our bodily eyes in some way the inconveniences of his infant needs, how he lay in a manger, how, with an ox and an ass standing by, he lay upon the hay where he had been placed." When the good and faithful man heard these things, he ran with haste and prepared in that place all the things the saint had told him.T
...The manger was prepared, the hay had been brought, the ox and the ass were led in. There simplicity was honored, poverty was exalted, humility was commended, and Greccio was made, as it were, a new Bethlehem.
Saint Francis of Assisi
Celano, First Life