"All the inhabitants of Canaan melted away" (Exodus 15:15). Once the inhabitants of Canaan heard that the Omnipresent had said to Moses, "Only from the cities of these peoples," and so forth, "for you shall utterly destroy them," and so forth, they said: these others and those others were afraid only on account of their money and on account of their possessions, but against us they are coming only to annihilate us and to inherit our land. They began to melt, as it is said, "melted away." And "melting" means nothing other than dissolving, as it is said, "the earth and all its inhabitants are dissolved" (Psalms 75:4), and it says, "so that the heart may melt" (Ezekiel 21:20).
All Canaan Melts in Fear of Utter Destruction
Yalkut Shimoni on Torah 251:14
נָמֹגוּ כֹּל יֹשְׁבֵי כְנָעַן. כֵּיוָן שֶׁשָּׁמְעוּ יוֹשְׁבֵי כְּנַעַן שֶׁאָמַר הַמָּקוֹם לְמֹשֶׁה, "רַק מֵעָרֵי הָעַמִּים הָאֵלֶּה" וְגוֹ' "כִּי הַחֲרֵם תַּחֲרִימֵם" וְגוֹ', אָמְרוּ אֵלּוּ וְאֵלּוּ לֹא הָיוּ מִתְיָרְאִים אֶלָּא מִפְּנֵי מָמוֹנָם וּמִפְּנֵי נִכְסֵיהֶם, אֲבָל עָלֵינוּ אֵין בָּאִין אֶלָּא לְכַלּוֹתֵנוּ וְלִירַשׁ אֶת אַרְצֵנוּ. הִתְחִילוּ נְמֵסִין שֶׁנֶּאֱמַר נָמֹגוּ אֵין נְמִיגָה אֶלָּא מְסִיָּה, שֶׁנֶּאֱמַר (תהלים עה, ד) "נְמוֹגִים אֶרֶץ וְכָל יֹשְׁבֶיהָ", וְאוֹמֵר (יחזקאל כא, כ) "לְמַעַן לָמוּג לֵב".