Do not redeem the firstborn animals

"But the firstborn of an ox or the firstborn of a sheep or the firstborn of a goat, you shall not redeem; they are holy. You shall sprinkle their blood on the altar and shall offer up their fat in smoke as an offering by fire, for a soothing aroma to the LORD.

Hebrew

יז אַךְ בְּכוֹר-שׁוֹר אוֹ-בְכוֹר כֶּשֶׂב אוֹ-בְכוֹר עֵז, לֹא תִפְדֶּה--קֹדֶשׁ הֵם: אֶת-דָּמָם תִּזְרֹק עַל-הַמִּזְבֵּחַ, וְאֶת-חֶלְבָּם תַּקְטִיר--אִשֶּׁה לְרֵיחַ נִיחֹחַ, לַיהוָה.

Greek

17 πλὴν πρωτότοκα μόσχων καὶ πρωτότοκα προβάτων καὶ πρωτότοκα αἰγῶν οὐ λυτρώσῃ· ἅγιά ἐστιν· καὶ τὸ αἷμα αὐτῶν προσχεεῖς πρὸς τὸ θυσιαστήριον καὶ τὸ στέαρ ἀνοίσεις κάρπωμα εἰς ὀσμὴν εὐωδίας κυρίῳ·

• Parashah: Korach
• Sefer HaChinuch: 393
• Mishneh Torah: Sacrifices — The Firstborn

• Numbers 18:17

Enumeration and classification from BibleData. The Greek is the Septuagint reading of the same verse, carried by the source for comparison.