A certain unlearned man asked Rabbi Meir: With what is a firstborn donkey redeemed? He said to him: With a lamb, as it is written, "And the firstling of a donkey you shall redeem with a lamb" (Exodus 34:20). And if he has no lamb, with what is it redeemed? He said to him: With a kid [a young goat]. He said to him: From where do you derive this? He said to him: As it is written, "This is the animal which you may eat: the ox, the sheep of the flock [seh kesavim], and the goat of the flock [seh izzim]" (Deuteronomy 14:4) [both are called seh, the word the redemption verse uses]. He stood up and kissed him on his head.
The Ignorant Man Who Kissed Rabbi Meir on the Head
Yalkut Shimoni on Torah 402:2
חַד עַם דְּאַרְעָא שְׁאָלֵיהּ לְרַבִּי מֵאִיר. פֶּטֶר חֲמוֹר, בְּמָה הוּא נִפְדֶּה. אָמַר לוֹ. בְּשֶׂה, דִּכְתִיב וּפֶטֶר חֲמוֹר תִּפְדֶּה בְשֶׂה. וְאִם אֵין לוֹ שֶׂה, בְּמָה הוּא נִפְדֶּה. אֲמַר לֵיהּ. בִּגְדִי. אֲמַר לֵיהּ מָן הָא. אֲמַר לֵיהּ. דִּכְתִיב (דברים יד, ד) "זֹאת הַבְּהֵמָה אֲשֶׁר תֹּאכֵלוּ שׁוֹר שֵׂה כְשָׂבִים וְשֵׂה עִזִּים". עָמַד וּנְשָׁקוֹ עַל רֹאֹשׁוֹ.