The Talmud (Brachos 24a) says that a husband's wife is like himself (eeshto kigufo). This has legal, ethical and metaphysical implications.
The principle that a couple are as one person shows up in practical Jewish law. I will bring four laws that demonstrate this clearly. The reason behind all four examples specifically is because of the principle "a wife is like himself" - as if the same body as the husband.
Evven Ha'Ezzer 83:a - When a person injures or disgraces another man's wife, part of the payment that the bais din (court) assesses in damages goes to the husband (not all of the settlement is paid to the wife who was the victim) because a wife is like himself (it is as if he was injured or disgraced as part of the assault or slander).
Orech Chayim 671:b - (in the laws of Chanuka, with Mishna Brura) Every member of the household is to light his own menora (candles), except the wife because a wife is like himself. This is in a case where the family is all home together. The wife is included in the husband's lighting of the menora.
Yora Daya 314:d - A wife does not testify against a husband in bais din because a wife is like himself. This excludes a case of divorce or abuse wherein the wife is bringing the husband to bais din.
Rambam Hilchos Ma'asay Korbonos 3:h - The laying upon the sacrificial animal excludes...one's servant and one's wife.
Hilchos Derech Eretz writes that laws which depend upon "his wife is like himself" demonstrate that oneness of a married couple surrounds all issues, times and circumstances in life. We see a central principle in the conduct of family life in general and marriage in particular. There are two aspects to the marriage relationship: 1. a husband and wife are as one person, and 2. they each have an independent individuality.
They each have a partial independent participation and identity in the wife's having been insulted, shamed or damaged (depending on the case, some portion of the settlement is assessed for payment to each spouse).
As part of the procedure for bringing a sacrifice at the Holy Temple which atones for sin, one lays one's hands and body-weight on the animal, e.g. an ox, for a moment just before it is to be slaughtered. One feels the life force of the animal which is about to be killed as an atonement for ones's sin. The Torah says that when the person does this laying upon the animal, he lays "his hand" on the animal. The Torah could have avoided writing "his," e.g. "a hand." The Talmud (Menachos 93b) says that in the Torah being so specific as to say "his hand," the Torah means ONLY HIS hand. The individual may not send a servant or an agent or his wife to replace or represent him, but he must personally place his own hand exclusively on the animal. He may place the hand of no one else - not even his wife - on the sacrifice. Since he did the sin, only he can do the atonement for it. Since the Torah NORMALLY PRESUMES THAT A WIFE IS LIKE HIMSELF, the Torah has to specify that in this isolated, unique case the sinner must place "his hand" on the animal during the atonement sacrifice procedure. Otherwise, you would think that a man could send his wife as his representative for the atonement sacrifice. IN THIS CASE, the Torah "goes out of its way" to specially teach that he may not make the otherwise normal presumption that "his wife is like himself." So powerful, central and axiomatic is the status of "his wife is like himself," for this exceptional law, the Torah has to specifically exclude the wife. Without "his," you would think a wife could place "her hand" on "his" sacrifice. When we don't have such a unique exception, one's "wife is like himself." To be continued.