The Ambrosian ms., with the Muratonian canon, has a work
Confessio fidei Catholicae, where the author is likely Isaac the Jew, writing around 370, connected with the AD 366 election dispute between Damasus and Urbanus.
This identification of Isaac the Jew as the author was explained by Dom Germain Morin, and affirmed by Cuthbert Hamilton Turner and Theodor Zahn, and three is a superb review by Andrew Eubank Burn.
Lewis Ayres of Durham affirms this authorship in:
Augustine and the Trinity, 2014
https://books.google.com/books?id=LpyG7YnkqokC&pg=PA99
p. 99-100.
While neither writing can be dated precisely, and both connect to Damasus, the quotation from Isaac the Jew is likely earlier than that of Priscillian by about
a decade.