פירוש על קידושין 3:5

The word “acquisition” is used because the law that betrothal can be effected with money is derived from the use of the word “taking” in two contexts—betrothal and the transfer of money when Abraham buys the field from Ephron. Since buying something is called an “acquisition” (two prooftexts are cited), taking a woman in betrothal is called, at least by this mishnah, “acquisition.”