Valerius Maximus 3.3 ext 1 (tr. D.R. Shackleton Bailey):
There is another strong and resolute soldiering of the spirit, powerful through letters, priestess of the venerable rites of learning, Philosophy. Once received in the heart, she drives away every unseemly and useless emotion, confirms its entirety with the bulwark of solid virtue, makes it more powerful than fear of pain.
Est et illa vehemens et constans animi militia, litteris pollens, venerabilium doctrinae sacrorum antistes, Philosophia. quae ubi pectore recepta est, omni inhonesto atque inutili adfectu dispulso, totum [in] solidae virtutis munimento confirmat, potentiusque metu facit ac dolore.
in del. Gertz
Related post: Hymn to Philosophy