(Genesis 23:13) There we learned: A woman is acquired in three ways: by money, by document, and by intercourse. By money, from where do we derive it? We learn it by a verbal analogy [gezeira shava] of "taking" and "taking" from the field of Ephron. It is written here, "When a man takes a woman and has relations with her" (Deuteronomy 24:1), and it is written there, "I have given the money of the field; take it from me" (Genesis 23:13). And "taking" is called an acquisition, as it is said, "the field that Abraham acquired" (Genesis 25:10); or alternatively, "fields shall be acquired with money" (Jeremiah 32:44). [Bracketed gloss: a gezeira shava is a tradition-based linkage of two passages through a shared term, here the verb "to take."]
How Betrothal by Money Is Learned From Ephron's Field
Yalkut Shimoni on Torah 102:18
(בראשית כג יג) תַּמָּן תָּנִינָן, הָאִשָּׁה נִקְנֵית בְּשָׁלֹשׁ דְּרָכִים, בְּכֶסֶף, בִּשְׁטַר וּבְבִּיאָה. בְּכֶסֶף, מִנָּא לָן, גָּמַר קִיחָה קִיחָה מִשְּׂדֵה עֶפְרוֹן, כְּתִיב הָכָא (דברים כד, א) "כִּי יִקַּח אִישׁ אִשָּׁה וּבְעָלָהּ" וּכְתִיב הָתָם נָתַתִּי כֶּסֶף הַשָּׂדֶה קַח מִמֶּנִי, וְקִיחָה אִיקְרֵי קִנְיָן, שֶׁנֶּאֱמַר (בראשית כה, י) "הַשָׂדֶה אֲשֶׁר קָנָה אַבְרָהָם", אִי נַמִּי "שָׂדוֹת בַּכֶּסֶף יִקְנוּ".