And the 28th mitzvah is that the priests are commanded to place [i.e. burn] the incense on the golden altar twice each day.

The source of this commandment is G‑d's statement1 (exalted be He), "Aaron shall burn upon [the altar] the incense of fragrant spices; every morning when he lights2 the lamps [of the menorah] he shall burn it. And towards evening, when Aaron lights the menorah, he shall burn it as a continual incense-offering."

The laws regarding this incense, how to make it and the description of how it was burned each day are explained in the beginning of Kerisus3 and in a number of places in tractate Tamid.4