Reading some of the passages from the Dhammapada (collected wisdom of the Buddha), I found some interesting parallels:
(1) “By one’s self the evil is done, by one’s self one suffers; by one’s self evil is left undone, by one’s self one is purified. The pure and the impure stand and fall by themselves, no one can purify another.”
This sounds exactly like the Stoicism of Marcus Aurelius, but also Jesus in the Gospels: “by your own words you shall be judged...by what measure you measure others, shall be measured unto you."
(2) “let a man, after he has discerned his own duty, be always attentive to his duty.”
Again, classic stoicism, but this sounds like Immanuel Kant's moral philosophy, who was obsessed with the concept of duty. Philosophy is finding out, by reason, what our duties are; and the truly good person does their duty for the sake of duty alone. Which reminds me of a much older saying: "know thyself, and do thy duty" [who said that?].
(3) “The virtuous man is happy in this world…”
Sounds like Aristotle, who thought the only road to true happiness was contemplating and practicing virtue constantly.
The Wisdom of the Buddha