Leaven on the Alter

Frankincense (also known as olibanum) is an aromatic resin used in incense and perfumes, obtained from trees of the genus Boswellia in the family Burseraceae. The word is from Old French franc encens ('high-quality incense').^[1]

Rambam Guide 3:46
To the above reason for the exclusive selection of the three kinds of animals for sacrifices, we may add the following, namely, that these species are animals which can be got very easily, contrary to the practice of idolaters that sacrifice lions, bears, and wild beasts, as is stated in the book Tomtom. As, however, many could not afford to offer a beast, the Law commanded that birds also should be sacrificed, but only of those species which are found abundantly in Palestine, are suitable, and can easily be obtained, namely, turtledoves and pigeons. Those who are too poor to offer a bird, may bring bread of any of the kinds then in use: baked in the oven, baked in a pan, or in a frying-pan. If the baking of the bread is too much trouble for a person, he may bring flour. All this concerns only those who desire to sacrifice; for we are distinctly told that the omission of the sacrificial service on our part will not be reckoned to us a sin: "If thou shalt forbear to vow, it shall be no sin in thee" (Deut. 23:22). The idolaters did not offer any other bread but leavened, and chose sweet things for their sacrifices, which they seasoned with honey, as is fully described in the books which I named before: but salt is not mentioned in any of their sacrifices. Our Law therefore forbade us to offer leaven or honey, and commanded us to have salt in every sacrifice: "With all thine offerings thou shalt offer salt" (Lev. 2:13). It is further ordained that the offerings must all be perfect and in the best condition, in order that no one should slight the offering or treat with contempt that which is offered to God's name: "Offer it now unto thy governor; will he be pleased with thee?" (Mal. 1:8). This is the reason why no animal could be brought that was not yet seven days old (Lev. 22:26); it is imperfect and contemptible, like an untimely birth. Because of their degraded character it was prohibited to bring "the hire of a harlot and the price of a dog" (Deut. 23:18) into the Sanctuary. In order to bring the offering in the beat condition, we choose the old of the turtle-doves and the young of the pigeons, the old pigeons being less agreeable. The oblation must likewise be mingled with oil, and must be of fine flour (Lev. 2:1), for in this condition it is good and pleasant. Frankincense is prescribed (ibid.) because its fumes are good in places filled with the odour of burnt flesh. The burnt-offering was flayed (Lev. 1:16), and its inwards and legs, although they were entirely burnt, had to be previously washed (ibid. ver. 9), in order that due respect should be shown to the sacrifice, and it should not appear despicable and contemptible. This object is constantly kept in view, and is often taught, "Ye say, The table of the Lord is polluted; and the fruit thereof, even his meat, is contemptible" (Mal. 1:12). For the same reason no body uncircumcised, or unclean (Lev. 22:4), was allowed to partake of any offering; nor could any offering be eaten that had become unclean (Lev. 7:19), or was left till after a certain time (ibid. 7:15-17), or concerning which an illegal intention had been conceived; and it had also to be consumed in a particular place. Of the burnt-offering, which is entirely devoted to God, nothing at all was eaten. Those sacrifices which are brought for a sin, viz., sin-offering and guilt-offering, must be eaten within the court of the Sanctuary (‘azarah), and only on the day of their slaughtering and the night following, whilst peace-offerings, which are next in sanctity, being sacrifices of the second degree, may be eaten in the whole of Jerusalem, on the day they have been offered and on the following day, but not later. After that time the sacrifices would become spoiled, and be unfit for food.