Bamidbar 9:3

ככל חקותיו ACCORDING TO ALL RITES OF IT [… SHALL YE KEEP IT] — This refers to the laws relating to its body itself (i.e. the animal itself) while alive — that it must be “a lamb, without blemish, a male, one year old” (Exodus 12:5) (Sifrei Bamidbar 65). וככל משפטיו AND ACCORDING TO ALL THE REGULATIONS THEREOF — This again refers to commands which have a bearing upon the animal itself but originating from another place (i.e. outside the animal itself), e.g. seven days for eating unleavened bread and during which the leaven must be removed from one’s home. [Some editions have (cf. Nachmanides): the laws relating to the animal itself are that it must be “a lamb, without blemish, a male and one year old”. Such as have to be practiced upon its body (note the difference in the meaning of this phrase, and the omission of ממקום אחר) are those mentioned in Exodus 12:9: “roasted with fire, its head with its legs and the inward parts thereof”; and finally such as go beyond the sacrifice itself: the eating of unleavened bread and the removal of leaven from the house].

בְּאַרְבָּעָ֣ה עָשָֽׂר־י֠וֹם בַּחֹ֨דֶשׁ הַזֶּ֜ה בֵּ֧ין הָֽעַרְבַּ֛יִם תַּעֲשׂ֥וּ אֹת֖וֹ בְּמֹעֲד֑וֹ כְּכׇל־חֻקֹּתָ֥יו וּכְכׇל־מִשְׁפָּטָ֖יו תַּעֲשׂ֥וּ אֹתֽוֹ׃

In the fourteenth day of this month, at evening, you shall keep it in its appointed season: according to all the rites of it, and according to all the ceremonies of it, shall you keep it.