"And every firstborn of man among your sons you shall redeem" (Exodus 13:13). Why is this stated? Because elsewhere it says, "And those to be redeemed, from a month old you shall redeem" (Numbers 18:16), which is a general statement, and "according to your valuation, five shekels of silver," which is a particular specification. In a case of a general statement followed by a particular, the general statement includes only what is in the particular. When it then says, "And every firstborn of man among your sons you shall redeem," it returns and states a general rule again. Should we then say it has gathered everything back into the first general statement? You say: no. Rather, in a case of general, particular, and general, you may infer only according to the character of the particular. Just as the particular speaks explicitly of property and movable goods that carry no real-estate liability, so too the general rule applies only to such. From here they said: a firstborn son may be redeemed with anything except slaves, deeds, land, and consecrated property. Rabbi says: a firstborn son may be redeemed with anything.
Redeeming the Firstborn Son With Movable Property
Yalkut Shimoni on Torah 225:1
וְכֹל בְּכוֹר אָדָם בְּבָנֶיךָ תִּפְדֶּה. לָמָּה נֶאֱמַר, לְפִי שֶׁהוּא אוֹמֵר (במדבר יח, טז) "וּפְדוּיָו מִבֶּן חֹדֶשׁ תִּפְדֶּה", כְּלָל, "בְּעֶרְכְּךָ כֶּסֶף חֲמֵשֶׁת שְׁקָלִים" פְּרָט, כְּלָל וּפְרָט אֵין בַּכְּלָל אֶלָּא מַה שֶּׁבַּפְּרָט, כְּשֶׁהוּא אוֹמֵר וְכֹל בְּכוֹר אָדָם בְּבָנֶיךָ תִּפְדֶּה חָזַר וְכָלַל, אוֹ כָּלַל בַּכְּלָל הָרִאשׁוֹן, אָמַרְתּ לָאו, אֶלָּא כְּלָל וּפְרָט וּכְלָל אִי אַתָּה דָּן אֶלָּא כְּעֵין הַפְּרָט, מַה הַפְּרָט מְפֹרָשׁ בִּנְכָסִין וּמִטַּלְטְלִין שֶׁאֵין לָהֶן אַחְרָיוּת אַף הַכְּלָל כֵּן. מִכָּאן אָמְרוּ, בַּכֹּל פּוֹדִין בְּכוֹר אָדָם חוּץ מִן הָעֲבָדִים וּשְׁטָרוֹת וְקַרְקָעוֹת וְהֶקְדָּשׁוֹת. רַבִּי אוֹמֵר, בַּכֹּל פּוֹדִין בְּכוֹרֵי אָדָם.