ablative of association
For reference, this is the NLG's explanation:
"The Ablative is often used with verbs of joining, mixing, clinging, exchanging; also with assuēscō, cōnsuēscō, assuēfaciō, and some others to denote association; as,—
improbitās scelere jūncta, badness joined with crime;
āēr calōre admixtus, air mixed with heat;
assuētus labōre, accustomed to (lit. familiarized with) toil;
pācem bellō permūtant, they change peace for (lit. with) war."
Thanks in advance!