Occasionally, I encounter people who think there was no true religious devotion in the pagan religions of the Graeco-Roman world. That is, that non-Christians did not show the same concern for honoring the gods that Second Temple Jews and nascent Christians did. However, evidence from papyri says otherwise.
For example, note the following papyrus, which is dated around the early second century CE. Although the papyrus is lacking information such as who composed it and to whom it was written, it is evidence that the author of the document desired the person to whom she/he was writing demonstrate his/her piety and attend a religious festival:
“The voyage past the Antaeopolite nome is most troublesome; every day I am burdened on account of it and I am extremely worn out with the matter. If a gratuity must be given to the brother of the mother of Achillas’ sons, please get some lotus (?) for him from Sarapion at my expense. Remember (μέμνη[σ]ο) the night-festival of Isis at the Serapeum” (P. Oxy 3.525; translation taken from Grenfield and Hunt, 3.262).
What we find in this papyrus is a window into the religious mind of the author. The author of this papyrus never thought that we (or anyone else for that matter) would read this private correspondence. Consequently, in a world where paper was expensive, people only took up precious space with matters of significance. Hence, we are able to see that a religious festival was of utmost importance for our author. This is evident in that not only did he/she bring up the topic, but also whoever composed this letter wanted, yea commanded the addressee to attend the religious festival of Isis, for the author used an imperative form of a verb to command the addressee not to forsake the assembly of the devotees of Isis at the Serapeum (“Remember (μέμνη[σ]ο) the night-festival of Isis at the Serapeum”), which was a temple dedicated to the god Sarapis and his female consort Isis. As a result, Paul would likely have made the same comment to the author of this papyrus and he did to the Athenians: “Athenians, I see how extremely religious you are in every way” (Acts 17.22).