Mishnah for Numbers 18:15
כָּל־פֶּ֣טֶר רֶ֠חֶם לְֽכָל־בָּשָׂ֞ר אֲשֶׁר־יַקְרִ֧יבוּ לַֽיהוָ֛ה בָּאָדָ֥ם וּבַבְּהֵמָ֖ה יִֽהְיֶה־לָּ֑ךְ אַ֣ךְ ׀ פָּדֹ֣ה תִפְדֶּ֗ה אֵ֚ת בְּכ֣וֹר הָֽאָדָ֔ם וְאֵ֛ת בְּכֽוֹר־הַבְּהֵמָ֥ה הַטְּמֵאָ֖ה תִּפְדֶּֽה׃
Every thing that openeth the womb, of all flesh which they offer unto the LORD, both of man and beast, shall be thine; howbeit the first-born of man shalt thou surely redeem, and the firstling of unclean beasts shalt thou redeem.
Mishnah Eduyot
Rabbi Joshua and Rabbi Zadok testified concerning the redemption (lamb) of a firstborn donkey, that if it died, the priest receives nothing, Whereas Rabbi Eliezer says: the owner must bear the responsibility as with the five selas [in the case] of a [firstborn] son. But the Sages say: he bears no responsibility any more than in the case of the redemption of second tithes.
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