What is the Covenant in the aayah “Those who break Allaah’s Covenant after ratifying it…”?

Abu Bakr ibn
al-‘Arabi said:

Covenants are
of two types: one for which expiation may be offered and another for
which there is no expiation. That for which expiation may be offered
is that which is intended as a vow to refrain from doing something or
to do something.

The second type
is a covenant in which the two parties are bound in a manner that is
permissible according to sharee’ah, and is binding, either exclusively
between them or amongst many people. It is not permissible to nullify
or abolish such a covenant, and it is not subject to kafaarah (expiation).
This is the covenant for which the one who breaks it will be gathered
(on the Day of Resurrection) as a betrayer, and a banner will be set
up for him commensurate with the degree of his betrayal, and it will
be said, “This is the betrayer of So and so.” Maalik says, a covenant
sworn by oath is not permitted to be nullified, and this is what is
meant by the aayah (interpretation of the meaning):

“and break
not the oaths after you have confirmed them — and indeed you have appointed
Allaah your surety”
[al-Nahl 16:91]

And this is a
matter concerning which there is no scholarly dispute.