Mark both those words, one and are, and thou wilt be delivered from Scylla and Charybdis. In that He says, one the Arian, in we are the Sabellian, is answered. There are both Father and Son. And if one, then there is no difference of persons between them.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Tract. xxxvi. non occ.