Saint Augustine of Hippo? He is pre-schism! Venerated by all who venerate saints!
Augustine, quoted on the Summa https://nostrcheck.me/media/1bcaf769395ec552ea5e15427ad78fadf6076543df3f9fd3d2900577621b50a0/06a3beb03361ec5446b462e6c1e1ffbe6caf1c0553dbaa5d532941d496d3c6d5.webp
I like that quote!!! Thank you!!
There are a lot of St. Augustine quotations on St. Thomas Aquinas works. I'm pretty sure he is the most quoted. Maybe you are familiarized with the Catena Aurea, a compilation of commentaries by the Church fathers. There are plenty quotes arguing the necessity of the Sacraments by authors like St. Jerome, St. John Chrysostom, St. Beda... This is my everyday reading: the daily Gospel and the commentaries on the Catena Aura about that passage