So much has been written in recent years on 'arra' in Justinian's law that one hesitates to add to it. But there is, I submit, a solution to the problem raised by the texts which is simpler than any so far suggested, and which gives a satisfactory result.
'Arra' in the Law of Justinian
Available at: https://digitalcommons.law.uga.edu/fac_artchop/396
Revue Internationale des Droits de l'Antiquite, Ser. 3, Vol. 6 (1959), pp. 385-389