Charles Ellicott Commentary Deuteronomy 15:4

"Howbeit there shall be no poor with thee; (for Jehovah will surely bless thee in the land which Jehovah thy God giveth thee for an inheritance to possess it;)" — Deuteronomy 15:4 (ASV)

Save when there shall be no poor (man) among you. — This clause is the source of a very interesting passage in the Acts of the Apostles. (Compare to Deuteronomy 4:34.) The passage from Acts states: Great grace was upon them all, for neither was there among them any (one) that lacked. The words at the beginning of the verse in Hebrew, “save when,” may also be rendered (as in the Margin) “to the end that,” or “to such an extent that there shall be no poor man among you.” Those who can well afford to pay need not be excused from their obligations.

For the Lord your God shall greatly bless you. — So in Acts 4:33, Great grace was upon them all. The blessing need not be equal and universal prosperity, if those who have the good things of this world will always remember the poor to such an extent that no member of the community will be left in want.