אז יבדיל. נָתַן לֵב לִהְיוֹת חָרֵד לַדָּבָר שֶׁיַּבְדִּילֵם, וְאַעַ"פִּ שֶׁאֵינָן קוֹלְטוֹת עַד שֶׁיֻּבְדְּלוּ אוֹתָן שֶׁבְּאֶרֶץ כְּנַעַן, אָמַר מֹשֶׁה מִצְוָה שֶׁאֶפְשָׁר לְקַיְּמָהּ אֲקַיְּמֶנָּה (מכות י'): אז יבדיל — The imperfect form יבדיל instead of הבדיל is to be thus explained (cf. Rashi on Exodus 15:1): He set his attention to be zealous for the matter, — to set them apart. And although they were not to serve as cities of refuge until those of Canaan proper (the western side of the Jordan) were set apart for that purpose, Moses said, Any duty that it is possible for me to perform I will perform (Makkot 10a).
בעבר הירדן מזרחה שמש. בְּאוֹתוֹ עֵבֶר שֶׁבְּמִזְרָחוֹ שֶׁל יַרְדֵּן: בעבר הירדן מזרחה שמש ON THE SIDE OF THE JORDAN TOWARDS THE SUN-RISING — i.e. on that side which is on the east of Jordan (not the side of the Jordan that is east of Canaan proper).
מזרחה שמש. לְפִי שֶׁהוּא דָּבוּק, נְקוּדָה רֵי"שׁ בַּחֲטָף, מִזְרָח שֶׁל שֶׁמֶשׁ – מְקוֹם זְרִיחַת הַשֶּׁמֶשׁ: מזרחה שמש — Because it (the word מזרחה) is in the construct state the ר is vowelled with Chataph (vocal Sheva), the meaning being, “the rising of the sun", i.e., the place of the sun's rising.