Halakha Ulangan 24:3: Shulchan Arukh, Even HaEzer & Mishneh Torah, Positive Mitzvot

וּשְׂנֵאָהּ֮ הָאִ֣ישׁ הָאַחֲרוֹן֒ וְכָ֨תַב לָ֜הּ סֵ֤פֶר כְּרִיתֻת֙ וְנָתַ֣ן בְּיָדָ֔הּ וְשִׁלְּחָ֖הּ מִבֵּית֑וֹ א֣וֹ כִ֤י יָמוּת֙ הָאִ֣ישׁ הָאַחֲר֔וֹן אֲשֶׁר־לְקָחָ֥הּ ל֖וֹ לְאִשָּֽׁה׃

lalu laki-laki yang kemudian itu membencinya, menulis surat cerai baginya, menyerahkannya ke tangannya, dan menyuruhnya pergi dari rumahnya, atau apabila laki-laki yang kemudian itu, yang telah mengambilnya menjadi istrinya, meninggal,

Shulchan Arukh, Even HaEzer

When he gives her the divorce document, he should say to her, "Behold you are divorced from me with this divorce document and permitted to [remarry] any other," or "Behold you are sent away from me." If his messenger gives it to her, he says, "Behold you are divorced from so-and-so with this divorce document, and behold you are permitted to [remarry] any other." If he says [instead], "I am not your spouse," or "I am not your husband," some say that is not a divorce, even if he discussed with her the process of the divorce, as it says (Deuteronomy 24:1, Deuteronomy 24:3) "And he sent her away", and not that he sent himself away. And some say that if he discussed the process of divorce with her, it is a divorce of doubtful [legality].
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Mishneh Torah, Positive Mitzvot

To divorce by a formal written document, as it is said, “And he shall write unto her a bill of divorcement and give it into her hand” (Deut. 24:1).
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Mishneh Torah, Positive Mitzvot

That the Court shall pass sentence of death by burning with fire as it is said, “They shall burn him and them with fire” (Lev. 20:14).
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