The Rambam’s Eleventh Principle: Parts of a Mitzvah are not Individual Mitzvos

Some mitzvos are made up of parts, like waving the four species on Succos. Waving all four species – lulav, esrog, hadassim and aravos - is a single mitzvah, not four mitzvos. Similarly, the Torah commands that six things be gathered for the purification process of the metzora (popularly translated as “leper,” but not really). These six things – two birds, scarlet, hyssop, cedar, spring water and a clay pot – are collectively ONE mitzvah.