Question: What is the source of Kidushin by giving money?

Answer: (Devarim 22, 13) "When (a man) will acquire (a woman)'' - (this teaches that) she is acquired by giving money.

Question: What is the source of Kidushin through marital relations?

Answer: (ibid) "...and he will have relations with her'' - (this teaches that) she is acquired through relations.

Question: I might assume that he must both give money and have relations. How do I know that one method works without the other?

R. Abahu citing R. Yochanan: (ibid, 22) "If a man will be found lying with a woman who is married to a husband (be'ulas ba'al)'' (i.e. they were married through relations). The Torah instructs that even if her husband only acquired her through relations, she incurs the punishment of strangulation if she is adulterous.

Similar to the Braisa: "...who is married to a husband''- this includes even a betrothed wife who had relations with her husband whilst still in her father's house - even though she is still considered merely betrothed, one who is adulterous with her incurs the punishment of strangulation (rather than stoning).] (Note: The Korban HaEidah adds this sentence, based on the parallel sugya in the 3rd Perek of Kesuvos.)

Not only is strangulation incurred for adultery if the husband had originally had relations with her in the regular way but even in the irregular way (i.e. from behind).

R. Abahu citing R. Yochanan: The pasuk is specifically needed to teach the case of the husband who had relations in the irregular way - if you say that it is needed for the case of relations in the regular way, why is this law true only if her husband had relations with her before the adultery...even someone else had done so, the same law (of strangulation) would apply?! And if this is so, why would the pasuk have said "be'ulas ba'al'' - it could have said "be'ulas ish'' - i.e. any man?!

Proof (Mishnah): If two had relations with her, the first incurs stoning and the second incurs strangulation.

Question: This only proves that he can acquire her with relations without money. But what about money without relations?

Answer: The pasuk states (Shemos 21, 11) in reference to a Jewish maidservant, "...and she shall leave free of charge, without payment''...and the previous pasuk states (21, 10), "if he shall take another addition to her'' (referring to a regular wife) - just as a maidservant is acquired with money, so is a wife.