"And they came to Elim, where there were twelve [springs of water and seventy palm trees]" (Exodus 15:27). This teaches that this place was praised for its water above all other places. Know that this is so, for there were twelve springs there, and they sufficed only for seventy palm trees; yet when Israel came and encamped upon them, six hundred thousand people, the springs supplied enough for the people and for the trees, and they did so twice and three times over. "And they encamped there beside the water." Israel never encamps except beside water, the words of Rabbi Yehoshua. Rabbi Elazar says: from the day the Holy One, blessed be He, created His world, He created twelve springs corresponding to the twelve tribes, and seventy palm trees corresponding to the seventy elders. And what does the verse teach by saying "and they encamped there beside the water"? It teaches that they were occupying themselves with the words of Torah that had been given to them at Marah.
Why Elim Had Twelve Springs and Seventy Palms
Yalkut Shimoni on Torah 257:5
(שמות טו כז) וַיָּבֹאוּ אֵילִמָה וְשָׁם שְׁתֵּים עֶשְׂרֵה וְגוֹ'. מַגִּיד שֶׁאוֹתוֹ מָקוֹם מְהוּלָּל בְּמַיִם יוֹתֵר מִכָּל הַמְּקוֹמוֹת. תֵּדַע שֶׁכֵּן, שֶׁהֲרֵי הָיוּ שָׁם שְׁנֵים עָשָׂר מַבּוּעִין וְלֹא סִפְּקוּ אֶלָּא לְשִׁבְעִים דְּקָלִים, וְכֵיוַן שֶׁבָּאוּ יִשְׂרָאֵל וְשָׁרוּ עֲלֵיהֶם שִׁשִּׁים רִבּוֹא אָדָם וְסִפְּקוּ לָהֶם וְלָנוּ וְשָׁנוּ וְשִׁלְּשׁוּ. וַיַּחֲנוּ שָׁם עַל הַמָּיִם. לְעוֹלָם אֵין יִשְׂרָאֵל שׁוֹרִין אֶלָּא עַל הַמַּיִם, דִּבְרֵי רַבִּי יְהוֹשֻׁעַ. רַבִּי אֶלְעָזָר אוֹמֵר, מִיּוֹם שֶׁבָּרָא הַקָּדוֹשׁ בָּרוּךְ הוּא אֶת עוֹלָמוֹ בָּרָא שְׁנֵים עָשָׂר מַבּוּעִין כְּנֶגֶד שְׁנֵים עָשָׂר שְׁבָטִים, שִׁבְעִים דְּקָלִים כְּנֶגֶד שִׁבְעִים זְקֵנִים, וּמַה תַּלְמוּד לוֹמַר וַיַּחֲנוּ שָׁם עַל הַמָּיִם, אֶלָּא מְלַמֵּד שֶׁהָיוּ עוֹסְקִין בְּדִבְרֵי תּוֹרָה שֶׁנִּתְּנוּ לָהֶן בְּמָרָה.