Don’t Beat Your Wife!
The Rabbeinu Simcha writes:
Regarding one who beats his wife, I find it acceptable that we should be exceptionally strict with such an individual and even more so than we are regarding one who beats another person. This is because one is not necessarily required to honor other people but one is required to honor one's wife – even more than oneself. One who does so [beats his wife] should be banned, excommunicated, lashed, and punished with every manner of force and even to cut off his hand if he does so regularly.
While this passage is certainly a strong voice of support for the proper treatment of women, it does, however, raise some serious questions. On what basis does Rabbeinu Simcha assert that one can cut off the hand of another person? The Torah certainly doesn’t allow such a thing! Indeed, the Shulchan Aruch, based on Talmudic sources, clearly delineates the procedures and payments that one who beats or injures another person is subject to, and cutting off hands is not one of them!
The source for Rabbeinu Simcha's ruling is from Rashi on his commentary to Sanhedrin 58b. Rashi writes:
They once sentenced a person, who regularly beat someone, to have his hand cut off. As it says earlier in this chapter (page 46a), the Beit Din would beat and punish people in ways not found in the Torah in order to protect and make a fence to ensure that transgressions don’t take place.
Make no mistake. When the Talmud, or any other authority, awards such powers to the "Beit Din," it does not refer to the rabbis or the Batei Din of today. Rather, it generally refers to the supreme Beit Din – the Sanhedrin – or a Beit Din in which all the members received the ancient classical semicha, both of which no longer exist today. It should also be noted that the members of such Batei Din were comprised of the most outstanding and pious rabbinical leaders of their generation. They were individuals who cared for every single Jew and had the highest regard for human life. Indeed, such Batei Din were known for making heroic efforts to find every possible excuse in order to avoid having to issue the death penalty, even when it was completely called for.
Not to worry. Such radical punishments are not and cannot be given out nowadays. But, yes, it is interesting to note that halacha allowed the Sanhedrin to take matters into their own hands, and to order violent punishment when called for. The message of this chapter: don't beat your wife. It's a sin and a terrible thing to do. But no, no one will be cutting off your hands.
 Cited in the Beit Yosef, EH 154.
 See Yevamot 62b.
 s.v. "ketz yada."
 See Makot 7a.
 For more on spousal abuse see Kaf Hachaim (Palagi) 1:11.