Another interpretation: It is the way of the world that a person empties a full vessel into an empty vessel; does one ever empty into a full vessel? So the whole world was water within water, yet you say "to one place"? Rather, from here we learn that the little holds the much. And similarly: "And Moses and Aaron gathered the assembly before the rock" (Numbers 20:10) — it was [only] as large as the opening of a small sieve, yet all Israel stood there; rather, from here we learn that the little holds the much. And similarly: "Take for yourselves handfuls" (Exodus 9:8) — now does the cupped hands [chofen] of Moses hold eight fistfuls [kemitzin]? The one who fills two cupped hands is not like the one who takes a single fistful, for the one who scoops with two hands holds double the one who takes one fistful; and it is written, "and Moses sprinkled it [threw it]" (Exodus 9:10). It turns out that the cupped hands of Moses held eight fistfuls — rather, from here we learn that the little held the much. And similarly: "And Joshua said: Come here and hear the words of the LORD" (Joshua 3:9) — he stood them between the two staves of the Ark.
How the Small Held the Great in Israel's History
Yalkut Shimoni on Torah 7:3
דָּבָר אַחֵר, בְּנֹהַג שֶׁבָּעוֹלָם אָדָם מְפַנֶה כְּלִי מָלֵא לְתוֹךְ כְּלִי רֵיקָן, שֶׁמָּא תּוֹךְ כְּלִי מָלֵא כָּךְ הָעוֹלָם כֻּלּוֹ מַיִם בְּמַיִם וְאַתְּ אַמְרְת אֶל מָקוֹם אֶחָד אֶלָּא מִכָּאן שֶׁהַמֻּעָט מַחֲזִיק אֶת הַמְּרֻבָּה. וְדִכְוָתֵהּ (במדבר כ, י) "וַיַקְהִלוּ משֶׁה וְאַהֲרֹן אֶת הַקָּהָל אֶל פְּנֵי הַסָּלַע", כִּמְלֹא פִּי כְּבָרָה קְטַנָּה הָיְתָה וְכָל יִשְרָאֵל עוֹמְדִין שָׁם, אֶלָּא מִכָּאן שֶׁהַמֻּעָט מַחֲזִיק אֶת הַמְּרֻבָּה. וְדִכְוָתֵהּ "קְחוּ לָכֶם מְלֹא חָפְנֵיכֶם" וְכִי חָפְנוֹ שֶׁל משֶׁה מַחֲזִיק שְׁמֹנָה קְמָצִים לֹא דָּמִי הַהוּא דְּחָפַן לְהַהוּא דְּקָמַץ דְּהַהוּא דְּחָפַן תְּרֵי כְּהַהוּא דְּקָמַץ, וּכְתִיב (שם) "וּזְרָקוֹ משֶׁה" נִמְצֵאת חָפְנוֹ שֶׁל משֶׁה מַחְזֶקֶת שְׁמֹנָה קְמָצִים אֶלָּא מִכָּאן שֶׁהֶחֱזִיק מֻעָט אֶת הַמְּרֻבָּה. וְדִכְוָתֵהּ (יהושע ג, ט) "וַיֹּאמֶר יְהוֹשֻׁעַ גּשׁוּ הֵנָּה וְשִׁמְעוּ אֶת דִּבְרֵי ה'", זְקָפָן בֵּין שְׁנֵי בַּדֵּי אָרוֹן.