In my past browsing of the suttas, I do not recall any teachings about giving & generosity that emphasize giving to the poor, apart from the duties of the Universal Monarch, which states:
And whosoever in thy kingdom is poor, to him let wealth be given.
Generally, most sutta teachings about giving are about giving to family, relatives, monks, deities, noble beings, etc. For example, well-known suttas about giving & benevolence, such as AN 4.61, AN 8.33, AN 8.35, AN 9.5 & DN 31 do not mention giving to the poor.
Since Buddhism emphasizes personal responsibility, including responsibility for society by earning income ethically, righteously or blamelessly, which includes responsibility towards employees, servants, local community, etc, it seems an emphasis upon the existence of a pool of chronically poor people is something Buddhism would prefer not to encourage.
For example, since Christianity strongly emphasizes giving charity to the poor for rebirth in heaven, it seems Christians have a vested personal interest in maintaining a pool of poor people, otherwise they would have no path to heaven; in the same way many left-wing government bureaucrats have a personal vested interest in maintaining social need in order to maintain their jobs.
The above said, after searching & searching just now, I found this sutta:
Now what, bhikkhus, is the kind of person who rains everywhere? Here, a certain person gives to all. He gives food, drink, clothing, vehicles, garlands, scents, ointments, beds, lodging, and lamps to all recluses and brahmins, to the poor, destitute, and needy. This is the kind of person who rains everywhere.
A person renowned for his bounty, Compassionate towards all beings, Distributes alms gladly. “Give! Give!” he says.
Like a great storm cloud That thunders and rains down Filling the levels and hollows, Saturating the earth with water, Even so is such a person.
