Jeremiah 51:63 Halakhah

וְהָיָה֙ כְּכַלֹּ֣תְךָ֔ לִקְרֹ֖א אֶת־הַסֵּ֣פֶר הַזֶּ֑ה תִּקְשֹׁ֤ר עָלָיו֙ אֶ֔בֶן וְהִשְׁלַכְתּ֖וֹ אֶל־תּ֥וֹךְ פְּרָֽת׃

And it shall be, when thou hast made an end of reading this book, that thou shalt bind a stone to it, and cast it into the midst of the Euphrates;