Reference for Yadayim 4:5

תַּרְגּוּם שֶׁבְּעֶזְרָא וְשֶׁבְּדָנִיֵּאל, מְטַמֵּא אֶת הַיָּדַיִם. תַּרְגּוּם שֶׁכְּתָבוֹ עִבְרִית וְעִבְרִית שֶׁכְּתָבוֹ תַּרְגּוּם, וּכְתָב עִבְרִי, אֵינוֹ מְטַמֵּא אֶת הַיָּדַיִם. לְעוֹלָם אֵינוֹ מְטַמֵּא, עַד שֶׁיִּכְתְּבֶנּוּ אַשּׁוּרִית, עַל הָעוֹר, וּבִדְיוֹ:

The [Aramaic] translations which are in [the books of] Ezra and Daniel render the hands impure. [Aramaic] translations written in Hebrew, and Hebrew written in translation or in [ancient] Hebrew characters, do not render the hands impure. They [i.e. sacred Scriptures] never render impurity, unless they are written in Assyrian [i.e. square] characters, on parchment, and with ink.

Jastrow