Deuteronomy 16:2,3

Thou shalt sacrifice the passover Strictly so called; which was the paschal lamb. The sheep and oxen here mentioned were additional sacrifices which were to be offered in the seven days of the paschal solemnity, Numbers 28:18. Indeed, the passage may be rendered, Thou shalt therefore observe the feast of the passover unto the Lord thy God with sheep and with oxen. Bread of affliction So called, because it was not pleasant nor easily digested, and was appointed to be used to put them in mind of their afflictions and miseries in Egypt, and of their coming out from thence in haste, being allowed no time to leaven or prepare their bread.