Source and decoding - Taanit 7a
לָמָּה נִמְשְׁלוּ דִּבְרֵי תוֹרָה כָּאֵשׁ, שֶׁנֶּאֱמַר: ״הֲלֹא כֹה דְבָרִי כָּאֵשׁ נְאֻם ה׳״, לוֹמַר לָךְ: מָה אֵשׁ אֵינוֹ דּוֹלֵק יְחִידִי, אַף דִּבְרֵי תוֹרָה אֵין מִתְקַיְּימִין בִּיחִידִי.
Rabbah bar bar Chanah: why are Torah words compared to fire, as it says "Is not My word like fire"? To teach: as fire does not burn alone, so Torah words do not endure with one alone.
Rabbah bar bar Chanah: why are Torah words compared to fire, as it says "Is not My word like fire"? To teach: as fire does not burn alone, so Torah words do not endure with one alone. Study with a partner sustains Torah.