rationalskepticism.org

The earliest conception of empathy explicitly seems to date back to the 19th century:

https://plato.stanford.edu/entries/empathy/#HisInt

The psychologist Edward Titchener (1867–1927) introduced the term “empathy” in 1909 into the English language as the translation of the German term “Einfühlung” (or “feeling into”), a term that by the end of the 19th century was in German philosophical circles understood as an important category in philosophical aesthetics. Even in Germany its use as a technical term of philosophical analysis did not have a long tradition. Various philosophers certainly speak throughout the 19th century and the second half of the 18th century in a more informal manner about our ability to “feel into” works of arts and into nature. Particularly important here is the fact that romantic thinkers, such as Herder and Novalis, viewed our ability to feel into nature as a vital corrective against the modern scientific attitude of merely dissecting nature into its elements;

Broader conceptions date back to antiquity:
https://en.wikipedia.org/wiki/Golden_Rule#Antiquity

Ancient Egypt

Possibly the earliest affirmation of the maxim of reciprocity, reflecting the ancient Egyptian goddess Ma'at, appears in the story of The Eloquent Peasant, which dates to the Middle Kingdom (c. 2040–1650 BC): "Now this is the command: Do to the doer to make him do."[14][15] This proverb embodies the do ut des principle.[16] A Late Period (c. 664–323 BC) papyrus contains an early negative affirmation of the Golden Rule: "That which you hate to be done to you, do not do to another."[17]