"And let them take a portion for Me" (Exodus 25:2). The One of whom it is said, "The earth is the LORD's and all that fills it" (Psalms 24:1), "to whom the sea belongs, for He made it" (Psalms 95:5), and, "Behold, to the LORD your God belong the heavens" (Deuteronomy 10:14), does He have need of flesh and blood? Rather, He desires Israel, to cause His Presence to dwell among them, like a father who longs for his children. Therefore it is said, "And let them take for Me." Now this is an argument from minor to major: if to make a Tabernacle, a glory and an atonement for Israel, the Holy One, blessed be He, said "Speak to the children of Israel" in a language of conciliation, as you say, "Speak to the heart of Jerusalem" (Isaiah 40:2), then the nations who oppress Israel and seize their money against their will, what shall become of them? For whoever seizes money is as though he sheds blood, as it is said, "because of the violence done to the children of Judah, in that they shed innocent blood in their land" (Joel 4:19). A certain heretic said to Rabbi Avin: "Your God is a priest, for it is written, 'And let them take a portion for Me.' When He buried Moses, in what did He immerse Himself? If you say in water, is it not written, 'Who measured the waters in the hollow of His hand?' (Isaiah 40:12)." He said to him: "In fire, for it is written, 'For behold, the LORD will come in fire' (Isaiah 66:15)." "But does immersion in fire count?" He said to him: "The essential immersion is in fire, for it is written, 'And everything that does not come into the fire you shall pass through water' (Numbers 31:23)."
Why God Who Owns Everything Asks Israel for an Offering
Yalkut Shimoni on Torah 363:9
וְיִקְחוּ לִי תְּרוּמָה. מִי שֶׁנֶּאֱמַר בּוֹ (תהלים כד, א) "לַה' הָאָרֶץ וּמְלוֹאָהּ" "אֲשֶׁר לוֹ הַיָּם וְהוּא עָשָׂהוּ", וְאוֹמֵר (דברים י, יד) "הֵן לַה' אֱלֹהֶיךָ הַשָּׁמַיִם", הוּא צָרִיךְ לְבָשָׂר וָדָם, אֶלָּא שֶׁחוֹמֵד לְיִשְׂרָאֵל לַשְׁרוֹת שְׁכִינָתוֹ בָּהֶם כְּאָב שֶׁמְּחַמֵּד לְבָנָיו, לְכָךְ נֶאֱמַר וְיִקְחוּ לִי. וַהֲרֵי דְּבָרִים קַל וָחֹמֶר וּמַה לַּעֲשׂוֹת מִשְׁכָּן כָּבוֹד וְכַפָּרָה לְיִשְׂרָאֵל אָמַר הַקָּדוֹשׁ בָּרוּךְ הוּא דַּבֵּר אֶל בְּנֵי יִשְׂרָאֵל בִּלְשׁוֹן פִּיּוּס כְּמָה דְּאַתְּ אָמַר (ישעיה מ, ב) "דַּבְּרוּ עַל לֵב יְרוּשָׁלַיִם", הָאֻמּוֹת שֶׁהֵן דּוֹחֲקִין לְיִשְׂרָאֵל וְנוֹטְלִים מָמוֹנָם עַל כָּרְחָן מַה תְּהֵא עֲלֵיהֶן, שֶׁכָּל מִי שֶׁנּוֹטֵל מָמוֹן כְּאִלּוּ שׁוֹפֵךְ דָּמִים שֶׁנֶּאֱמַר "מֵחֲמַס בְּנֵי יְהוּדָה אֲשֶׁר שָׁפְכוּ דַּם נָקִיא בְּאַרְצָם". אֲמַר לֵיהּ הַהוּא מִינָאָה לְרַבִּי אָבִין, אֱלֹהֵיכֶם כֹּהֵן הוּא, דִּכְתִיב וְיִקְחוּ לִי תְּרוּמָה, כִּי קָבַר לְמֹשֶׁה בְּמַאי טָבַל, אִילֵימָא בְּמַיָּא, וְהָכְתִיב (ישעיה מ, יב) "מִי מָדַד בְּשָׁעֳלוֹ מַיִם". אֲמַר לֵיהּ, בְּנוּרָא, דִּכְתִיב "כִּי הִנֵּה ה' בְּאֵשׁ יָבֹא". וּמִי סַלְקָא טְבִילָה בְּנוּרָא. אֲמַר לֵיהּ, עִקָּר טְבִילוּתָא בְּנוּרָא, דִּכְתִיב (במדבר לא, כג) "וְכֹל אֲשֶׁר לֹא יָבֹא בָאֵשׁ תַּעֲבִירוּ בַמָּיִם".