Apastambadharmasutra 2.4.9

And on the following day (he shall search for him), feast him to his heart's content, and accompany him (on his departure).

(If the guest) possesses a carriage, (he shall accompany him) as far as that.

Any other (guest he must accompany), until permission to return is given.

If (the guest) forgets (to give leave to depart), the (host) may return on reaching the boundary of his village.

To all (those who come for food) at (the end of) the Vaisvadeva he shall give a portion, even to dogs and Kandâlas.

Some declare that he shall not give anything to unworthy people (such as Kandâlas).

A person who has been initiated shall not eat the leavings of women or of an uninitiated person.

All gifts are to be preceded by (pouring out) water.

(But gifts offered to priests) at sacrifices (are to be given) in the manner prescribed by the Veda.

The division of the food must be made in such a manner that those who receive daily portions (slaves) do not suffer by it.

At his pleasure, he may stint himself, his wife, or his children, but by no means a slave who does his work.

And he must not stint himself so much that he becomes unable to perform his duties.

Now they quote also (the following two verses):
'Eight mouthfuls are the meal of an ascetic, sixteen that of a hermit living in the woods, thirty-two that of a householder, and an unlimited quantity that of a student. An Agnihotrin, a draught-ox, and a student, those three can do their work only if they eat; without eating (much), they cannot do it.'