'Obligation' in the Bible

But if a widow has children or grandchildren [who are adults], see to it that these first learn to show great respect to their own family [as their religious duty and natural obligation], and to compensate their parents or grandparents [for their upbringing]; for this is acceptable and pleasing in the sight of God.

If anyone fails to provide for his own, and especially for those of his own family, he has denied the faith [by disregarding its precepts] and is worse than an unbeliever [who fulfills his obligation in these matters].