The great Hispano-Roman thinker and courtier Seneca (circa 4 B.C. to 65 A.D.) gives us many fine quotes (notice the dates that make him literally contemporaneous with Jesus of Nazareth, who was also born circa 4 B.C. and executed, at a much younger age, on the cross circa 30/33 A.D.).
I will focus (today, at least) on just one quote found in No. 88 of his Moral Epistles:
Kindliness [Humanitas] forbids you to be over-bearing towards your associates, and it forbids you to be grasping. In words and in deeds and in feelings it shows itself gentle and courteous to all men. It counts no evil as another's solely. And the reason it loves its own good is chiefly because it will some day be the good of another.
Seneca, Epistulae Morales LXXXVIII, Section 30, trans. R.M. Gummere, Loeb Classical Library (bold emphasis added).
I want to focus on the words in bold print telling us that kindliness or compassion "counts no evil as another's solely" (Nullum alienum malum putat; "It thinks no evil foreign").
A friend once retorted that my expressions of sympathy were mere pity, with the unspoken implication that such pity was somehow a second best. I immediately responded that it was not a matter of "pity," but rather of compassion.
Well, Seneca defines compassion for us: we take on the evil suffered by the other. Our common humanity unites us as suffering beings, everyone of us (Buddhists will find this very familiar). To be compassionate is to come near and to recognize that bond and kinship.
Pity, on the other hand, can have, to some, connotations of condescending distance. Compassion is far from that distant condenscion but rather takes on the suffering of the other as one's own. There is no distance.
(Medieval image of Plato, Seneca, and Aristotle, from left to right, in public domain)