I run into this sentence of the Digest - D.9.2.54
Legis Aquiliae debitori competit actio, cum reus stipulandi ante moram promissum animal vulneraverit.
I understand that the person who has promessed (reus stipulandi) [to deliver] an animal injured it before the moment he was due to deliver it. In that case, the debtor (i.e. the buyer who owes payment of the purchase price) has the action of the lex Aquilia against the sellor.
Not sure my understanding is correct.