I might think (that they take poor-tithe) whether or not they are "children of the covenant"; it is, therefore, written (Ibid.) "and the Levite" — Just as the Levite is a "child of the covenant," so, all must be "children of the covenant."
"and they shall eat and be sated": Give them enough to be sated — whence they ruled: The poor man is not to be given less in the threshing floor than a half kav of wheat or a kav of barley.
"who are in your gates": We are hereby taught that we do not send the poor out (of Eretz Yisrael to earn a living.)