Now, the source for the seeming adage against teaching women Torah is found in Sotah 20a.
- יש זכות תולה שנה אחת יש זכות תולה ב' שנים יש זכות תולה ג' שנים מכאן אומר בן עזאי חייב אדם ללמד את בתו תורה שאם תשתה תדע שהזכות תולה לה ר"א אומר כל המלמד בתו תורה <כאילו> לומדה תפלות ר' יהושע אומר רוצה אשה בקב ותפלות מט' קבין ופרישות הוא היה אומר חסיד שוטה ורשע ערום ואשה פרושה ומכות פרושין הרי אלו מבלי עולם:
- IF SHE POSSESSED A MERIT, IT [CAUSES THE WATER] TO SUSPEND ITS EFFECT UPON HER. SOME MERIT SUSPENDS THE EFFECT FOR ONE YEAR, ANOTHER FOR TWO YEARS, AND ANOTHER FOR THREE YEARS. HENCE DECLARED BEN AZZAI, A MAN IS UNDER THE OBLIGATION TO TEACH HIS DAUGHTER TORAH, SO THAT IF SHE HAS TO DRINK [THE WATER OF BITTERNESS], SHE MAY KNOW THAT THE MERIT SUSPENDS7 ITS EFFECT. R. ELIEZER SAYS: WHOEVER TEACHES HIS DAUGHTER TORAH TEACHES HER OBSCENITY. R. JOSHUA SAYS: A WOMAN PREFERS ONE KAB8 AND SEXUAL INDULGENCE TO NINE KAB9 AND CONTINENCE. HE USED TO SAY, A FOOLISH PIETIST, A CUNNING ROGUE, A FEMALE PHARISEE, AND THE PLAGUE OF PHARISEES10 BRING DESTRUCTION UPON THE WORLD.
The Soncino translation uses the word obscenity, though most times the word tiflus is associated more with "foolishness."
So what's going on in this passage? This is a mishna in Sotah that's explaining what happens when the woman drinks the bitter waters. She will not even finish drinking before her face turns pale, her eyes start to bulge, her body swells up, and they have to move her so she doesn't die in the ezra and make the ezra tamei (it's a tumah d'rabanan.) Sometimes the water might not work this quickly. This is because the woman has a merit. Some merits work for keeping her alive one year, others two, perhaps more.
Based on this, Ben-Azai says, "A man is obligated to teach his daughter Torah so that she knows this isn't all nonsense." Otherwise, the daughter might think- I actually committed the sin, drank the water, and got off scot-free! I can fool the sotah waters! The man has to teach his daughter this is not the case, but rather she has a merit that is keeping her alive for a while longer (eventually, however, she will die.)
R' Eliezer says that anyone who teaches his daughter Torah teachers her tiflus (foolishness, obscenity.)
R' Yehoshua further comments that women would rather have a small income and sexual relations than a lot of money and the husband never being around! (which sounds quite reasonable)
R' Yehoshua used to say there are all types of people who destroy the world.
Chassid Shoteh- This is like the man who sees a woman drowning and won't save her because he's "too frum"
Rasha Arum- Sly and wicked evildoer
Isha Perusha- The woman who pretends to be pious but is really involved in illegal activities
Makos Perushin- The self-flagellating, mortification-of-the-flesh kind of people- people who think this makes them pious, when it is not really true