Another interpretation: "the far side of the wilderness" — it brought him tidings that his flock would be consumed in the wilderness, and he would be gathered together with them. "And the angel of the LORD appeared unto him in a flame of fire" (Exodus 3:2). Why in a flame of fire [belabbat esh]? In order to embolden his heart [lelabevo], so that when he would come to Sinai and see the fire he would not be afraid.
The Flame That Readied the Heart of Moses for Sinai
Yalkut Shimoni on Torah 169:9
דָּבָר אַחֵר, אַחַר הַמִּדְבָּר, בִּשְּׂרוֹ שֶׁצֹּאנוֹ כָּלֶה בַּמִדְבָּר, וְהוּא עִמָּהֶם נֶאֱסַף. וַיֵּרָא מַלְאַךְ ה' אֵלָיו בְּלַבַּת אֵשׁ, לָמָּה בְּלַבַּת אֵשׁ, כְּדֵי לְלַבְּבוֹ כְּשֶׁיָּבֹא לְסִינַי וְיִרְאֶה הָאֵשׁ וְלֹא יִתְיָרֵא.