The manuscript Ambrosianus E 49-50 inf. was created to serve as a a mastercopy of the Orations of Gregory of Nazianzus that would give order to the complicated tradition of the text and its scholia and show itself an excellent model of the highest level of book production. Both its apparatus of variant readings and the scholia transcribed in the margins, on the one hand, and the meticulous correction of the text carried out by the main scribe, on the other, attest to considerable philological acumen. The solid method and the learning they show lead us back to the very origins of the tradition of our texts, and then guide us down through their later history during the Byzantine centuries. Moreover, the Ambrosianus displays a distinctive physiognomy that distinguishes it from the other «critical» witnesses for Gregory’s oeuvre. To be precise, it seems to belong to a milieu that was probably strongly marked by the cult of saint Basil of Caesarea.