Numbers 9:11

9:11 They may observe it on the fourteenth day of the second month at twilight; they are to eat it with bread made without yeast and with bitter herbs.

Numbers 28:17

28:17 And on the fifteenth day of this month is the festival. For seven days bread made without yeast must be eaten.

Numbers 29:2

29:2 You must offer a burnt offering as a sweet aroma to the Lord: one young bull, one ram, and seven lambs one year old without blemish.