[PAULUS libro tertio ad edictum. ] §2.14.2.prLabeo ait conuenire posse uel re: uel per epistulam uel per nuntium inter absentes quoque posse.
[PAUL, On the Edict, book 3] Labeo says that agreement can be made either by act, or also between absent persons either by letter or by messenger.
sed etiam tacite consensu conuenire intellegitur: §2.14.2.1et ideo si debitori meo reddiderim cautionem, uidetur inter nos conuenisse ne peterem, profuturamque ei conuentionis exceptionem placuit.
But it is also understood that agreement is reached tacitly by consent; and therefore, if I return a written acknowledgment of debt to my debtor, it seems that there has been an agreement between us that I would not sue, and it has been decided that the exception of agreement shall benefit him.