In Looking for The Stranger (University of Chicago Press, 2016), Alice Kaplan points out (on page 11) that Camus received his philosophy degree at the University of Algiers
with a thesis on Plotinus and the early Saint Augustine. There is a specific detail in Saint Augustine's Confessions that finds a parallel in Meursault's behaviour:
miserable over the death of his mother, Augustine refuses to weep at her funeral, and looks for a cure to his sorrow by going to the baths.
Below are a few relevant passages from Augustine's Confessions:
Chap. XII. — How he mourned his dead mother.
- I closed her eyes; and there flowed a great sadness into my heart, and it was passing into tears, when mine eyes at the same time, by the violent control of my mind, sucked back the fountain dry, and woe was me in such a struggle! But, as soon as she breathed her last, the boy Adeodatus burst out into wailing, but, being checked by us all, he became quiet. In like manner also my own childish feeling, which was, through the youthful voice of my heart, finding escape in tears, was restrained and silenced.
- (...) So, when the body was carried forth, we both went and returned without tears. For neither in those prayers which we poured forth unto Thee when the sacrifice of our redemption was offered up unto Thee for her,— the dead body being now placed by the side of the grave, as the custom there is, prior to its being laid therein,— neither in their prayers did I shed tears; (...)
It appeared to me also a good thing to go and bathe, I having heard that the bath [balneum] Took its name from the Greek βαλανεῖον because it drives trouble from the mind.
Book IX, Chapter XII.
Obviously, Camus did not copy Augustine's behaviour one-to-one: we know more about Augustine's reasons for withholding his tears than about Meursault's, even though both the Confessions and The Strange are first-person narratives. Augustine goes to the baths on the same day as the funeral, whereas Meursault goes swimming on the next day. Augustine didn't meet a former colleague and did not go to the cinema, let alone watch a film with Fernandel. However, the parallels are close enough to make the plausible claim that Camus took inspiration for this from Augustine's Confessions.