TSK · Numbers 9:3

And ye shall keep it up until the fourteenth day of the same month: and the whole assembly of the congregation of Israel shall kill it in the evening.

The fourteenth day of the second month at even they shall keep it, [and] eat it with unleavened bread and bitter [herbs].

Then they killed the passover on the fourteenth [day] of the second month: and the priests and the Levites were ashamed, and sanctified themselves, and brought in the burnt offerings into the house of the LORD.