כִּי־רַבַּ֥ת בַּקָּהָ֖ל אֲשֶׁ֣ר לֹא־הִתְקַדָּ֑שׁוּ וְהַלְוִיִּ֞ם עַל־שְׁחִיטַ֣ת הַפְּסָחִ֗ים לְכֹל֙ לֹ֣א טָה֔וֹר לְהַקְדִּ֖ישׁ לַיהוָֽה׃
For there were many in the congregation that had not sanctified themselves; therefore the Levites had the charge of killing the passover lambs for every one that was not clean, to sanctify them unto the LORD.
English Explanation of Mishnah Pesachim
The Israelite killed [the lamb]; If an Israelite wishes to slaughter his own pesah he may do so. Most other sacrifices are slaughtered only by priests. However, in Ezra 6:20 and II Chronicles 30:17, 35:6,11, the Levites are those who slaughter the pesah.