Saint Gall, Stiftsbibliothek 673, p. 170

His ita respondetur quibus sic obicitur: Consensus est duorum uel plurium sensus in idem.  Qui autem errat non consentit, nec ergo simul cum alio sentit (Consent is the agreement of two or more in the same thing.  Who errs, moreover, does not consent, and therefore does not agree with the other at the same time).

Justinian, Digest  2.14.1.2:  Ulpianus 4 ad ed. Et est pactio duorum pluriumve in idem placitum et consensus.

Justinian, Digest 50.12.3pr. Ulpianus 4 disp. Pactum est duorum consensus atque conventio.