כְּעַ֣ן מַלְכָּ֔א תְּקִ֥ים אֱסָרָ֖א וְתִרְשֻׁ֣ם כְּתָבָ֑א דִּ֣י לָ֧א לְהַשְׁנָיָ֛ה כְּדָת־מָדַ֥י וּפָרַ֖ס דִּי־לָ֥א תֶעְדֵּֽא׃
Now, O king, establish the interdict, and sign the writing, that it be not changed, according to the law of the Medes and Persians, which altereth not.’
Rashi on Daniel
you shall issue a decree lit. you shall put up this decree.
Rashi on Daniel
that will not be amended that will not be amended, like the law of Media and Persia.