שִׁמְעוֹן הַצַּדִּיק הָיָה מִשְּׁיָרֵי כְנֶסֶת הַגְּדוֹלָה. הוּא הָיָה אוֹמֵר, עַל שְׁלשָׁה דְבָרִים הָעוֹלָם עוֹמֵד, עַל הַתּוֹרָה וְעַל הָעֲבוֹדָה וְעַל גְּמִילוּת חֲסָדִים:
Shimon the Righteous was one of the last of the men of the great assembly. He used to say: the world stands upon three things: the Torah, the Temple service, and the practice of acts of piety.
אמר הני מערב רב קא אתו דכתיב (דברים יג, יח) ונתן לך רחמים ורחמך כל המרחם על הבריות בידוע שהוא מזרעו של אברהם אבינו וכל מי שאינו מרחם על הבריות בידוע שאינו מזרעו של אברהם אבינו
He said: These wealthy people are not descendants of our forefathers, but they came from the mixed multitude, as it is written: “And show you compassion, and have compassion upon you, and multiply you, as He has sworn to your fathers” (Deuteronomy 13:18), from which it is derived: Anyone who has compassion for God’s creatures, it is known that he is of the descendants of Abraham, our father, and anyone who does not have compassion for God’s creatures, it is known that he is not of the descendants of Abraham, our father. Since these wealthy Babylonians do not have compassion on people, clearly they are not descended from Abraham, Isaac, and Jacob.
Of the countless Jewish texts about compassion that I could have chosen, I think these two most clearly spell out the Jewish position on compassion: It is one of the pillars on which the entire world rests, and if you’re not compassionate, you’re not truly a Jew. (The latter statement obviously isn’t meant to be taken literally, but I very much agree with the sentiment.)