From the Vitae Fratrum:
WHEN the brethren were still at St Sixtus, and numbered one hundred, St Dominic on a certain day told Brother John of Calabria and Brother Albert of Rome to go and beg alms in the city. After they had been begging from early morning to three in the afternoon without obtaining anything, they returned home empty-handed. But as they passed the church of St Anastasia, a woman met them who had a great devotion for the Order, and seeing that they had procured no alms she gave them a loaf of bread, saying: 'I won't have you go home empty-handed.' They took the loaf and were journeying home wards, when lo, a youth of comely mien and dressed in white joined them and asked for an alms. They began to excuse themselves by saying they could not afford to give him anything as they had not enough for themselves. But as he pleaded yet more urgently they said each to the other: 'What are we to do with only one loaf? let us bestow it on him for the love of God"; so they gave him the loaf, and directly after he disappeared, nor could they discover whither he had gone.
On their return home our holy father met them, and knowing all that had passed, by a special revelation of the Holy Ghost, he said to them, with a beaming face: 'My sons, have you nothing at all?' But they answered: 'Truly we have nothing, father:' They then rehearsed what had befallen them, and told him all about the poor man on whom they had bestowed the loaf. To this he replied: 'It was an angel of God; but the Lord will feed his servants: let us betake ourselves to prayer.' He went to the church, and after a short space came out and bade them call together the community for dinner. Upon this they answered him: 'But, holy father, why do you wish to bring them here since we have nothing to set before them.' Yet as he foreknew what would happen, he simply said: 'The Lord will feed his servants.' Now as they tarried in doing as he bid them, he called Brother Roger the cellarer and told him to call the brethren to table, as the Lord would provide for his servants.
The tables were at last spread and the cups set in order, the signal was given and they entered the refectory. When the brethren were seated our holy father blessed the table, and Brother Henry of Rome began the reading as is the custom during dinner. But St Dominic joined his hands and began to pray over the table, and lo, as he had promised by the promptings of the Holy Ghost, there suddenly appeared, by God's providence, two very handsome youths in the middle of the refectory, carrying upon their shoulders two clean linen cloths filled with white loaves. Then, starting with the lowest one on the right side and the other on the left, they set a whole loaf of rare beauty before each of the brethren. When they came to St Dominic they in like manner set a whole loaf before him, and then, bowing their heads, they disappeared, and to this day no one knows whence they came or whither they went.
Then St Dominic said: 'My sons, eat the bread which the Lord has sent us.' He then bade the servers pour out wine for the brethren, but they replied: 'Holy father, we have none.' Then full of the spirit of prophecy he said to them: 'Go to the cask and give the brethren the wine to drink which our Lord has sent them.' So they went as he had bidden them, and found the cask brimful of the best wine, and drawing a measure they carried it to the brethren. Upon this St Dominic said to them: 'My brothers, drink the wine which the Lord hath sent us.' They ate and drank as much as they pleased that day, and the next day, and again a third day.
After dinner then he had all that was left of the bread and wine given to the poor, and would not suffer any of it to be kept in the house. He did not send them out for alms during those three days, since the Lord had abundantly provided them with bread and wine from heaven. After this the holy father made to them a beautiful sermon, and warned them never to distrust God's providence even in time of want.
Brother Tancred, the prior of the brethren, Brother Odo of Rome, Brother Henry of the same place, Brother Laurence from England, Brother Gaude, Brother John of Rome, and many more were present and told this striking miracle to Sister Cecilia and the other nuns, at the time she was yet staying in St Mary's monastery beyond the Tiber. They gave the sisters some of the bread and wine which they preserved for many years as relics.