Halakha Imamat 6:2: Mishneh Torah, Prayer and the Priestly Blessing & Sefer HaChinukh

So also they ordained that a person should recite one service of Prayer at night, since the portions of the animal offered up as the Afternoon Sacrifice were consumed on the altar throughout the night, as it is said, "This is the law of the burnt offering; this it is that which goeth up on its firewood upon the altar all night" (Leviticus 6:2). And in this sense it is said, "Evening and morning and at noon will I meditate and cry aloud, and He hath heard my voice" (Psalms 55:18). The Evening Service is not obligatory like the Morning and Afternoon Services. Nevertheless all Israelites, wherever they have settled, have adopted the practice of reciting the Evening Service and have accepted it as obligatory.

Ezra instituted the rule for Israel that the portion containing the Imprecations in the book of Leviticus (26:3-end of book) should be read before the feast of Pentecost; and those in the book of Deuteronomy (26:1-29:8) before the New Year. The prevalent custom is to read the portion Bemidbar Sinai (Numbers 1:1-4:20) before Pentecost; Vaethchanan (Deuteronomy 3:23-7:11) after the Ninth of Ab; Atem Nitzabim (Deuteronomy 29:9-30:20) before the New Year; Tzav ess Aharon (Leviticus 6:1-8:36) before Passover in an ordinary year (of twelve months). Hence, on some Sabbaths, two portions are read during the morning service, for example, Isha Ki Tazria (Leviticus 12:1-13:59) and Vezoth tihejeh Torath Hametzora (ibid. 14:1-15:33); Bechukotai (ibid. 26:3-end of book) and Behar Sinai (ibid. 25:1-26:2) etc.; the purpose being to ensure that the reading of the Pentateuch shall be completed in one year and that the portions above mentioned shall be read at their appointed periods.

To not leave the entrails of the Pesach sacrifice to stay overnight: Not to leave the entrails of the Pesach sacrifice until the morning, [such] that they not be sacrificed, and [so] become disqualified with this leaving over and become called notar (what is left over); as it is stated (Exodus 23:18), “and the fat of My festival offering shall not be left lying until morning.” And the same is true of other portions to be burned in other sacrifices. And the language of Mekhilta DeRabbi Yishmael 23:18 is “‘The fat shall not be left lying’ — the verse comes to teach that the fats are disqualified by lying over.” And this preventing was already repeated in another place, as it is stated (Exodus 34:25), “and the sacrifice of the festival of Pesach shall not be left lying until morning.”