It is ordained that God commands justice and goodness towards relatives and forbids immorality and injustice, and covenant made needs to be fulfilled, and an oath kept:
‘’God commands justice, and goodness, and generosity towards relatives. And he forbids immorality, and injustice, and oppression, He advises you, so that you may take heed’’ (16:90)
Relatives assume priority in the wider base of humanity. It is often said that charity begins at home. Hence justice, goodness, and generosity have to start from near and dear ones before dispensing them to the humanity at large. The relative may be taken in its wider sense.
Dispensing justice, goodness, and generosity, while avoiding the forbidden-- immorality, and injustice, and oppression is to fulfil the covenant of God. Once made, the sanctity of the covenant has to be maintained.
It is akin to an oath, which once ratified, cannot be broken. God almighty stands as the Guarantor of a covenant, and of an oath—a Guarantor, Who knows what to do, in case the sanctity of a covenant, of an oath is violated:
‘’Fulfil the covenant of God when you make a covenant, and do not break oaths after ratifying them. You have made God your Guarantor, and God knows what to do’’ (16:91)
The Divine Commands that Ayahs (16:90 & 16:91) pertain to could be inferred as:
(1) Do justice to all
(2) Make good the deficiencies of others beginning with those nearest to you, whether relatives or others
(3) Avoid accumulating everything for your own self
(4) Avoid that which is not recognized by Quran to be good
(5) Do not transgress the limits set by Allah
(6) Fulfil the covenant after having confirmed them particularly when you have made Allah a surety with you
(7) Do not break oaths after you have made Allah as a surety for them