Charles Ellicott Commentary Leviticus 14:4

"then shall the priest command to take for him that is to be cleansed two living clean birds, and cedar wood, and scarlet, and hyssop:" — Leviticus 14:4 (ASV)

“Then the priest is to command to take”: Literally, And the priest shall command, and he shall take, meaning the leper is to do the taking. To avoid ambiguity about who this refers to, the translators of the Authorized Version adopted the rendering in the text. As the relatives of the cured leper procured the items prescribed for the purification, some ancient versions render it, And they shall take.

Two birds alive and clean. These were either sparrows, doves, turtledoves, or any other birds, provided they belonged to the clean species described in Leviticus 11. According to the canons that prevailed during the Second Temple period, the birds had to be sparrows. The reason given for this was that since leprosy was regarded as a divine punishment for slander, birds known for their constant twittering were selected. This explains the rendering of “sparrow” in the Latin Vulgate and in the margin of the Authorized Version.

And cedar wood. This had to be a foot and a half long, and its thickness a quarter of that of a bed’s foot-post. Although this wood was primarily chosen for its antiseptic properties, which made it especially suitable for the occasion, it also—belonging to the loftiest of trees (Psalms 2:13,Psalms 27:24; Amos 2:9)—was intended to symbolize the haughtiness of mind that called down the affliction of leprosy.

And scarlet. This was probably a band of scarlet wool with which the cedar and the hyssop were tied together. In later times, the woolen band had to be the weight of a shekel, or weigh thirty-two grains of barley. It was understood to symbolize the purified and now healthy blood.

And hyssop. This, according to the canons that prevailed in the time of Christ, had to be at least a handbreadth in size. It could not be the so-called Greek, ornamental, Roman, or wild hyssop, or any other hyssop distinguished by the name of the place where it grew. Instead, it had to be the common hyssop that grew in gardens. Though, like the cedar wood, it was primarily used on these occasions for its aromatic properties, this diminutive shrub was also most likely intended to symbolize the humility of the cured leper.

Hence, ancient tradition tells us, “Cedar wood and hyssop, the highest and the lowest, give the leper purity. Why these? Because pride was the cause of the disease, which cannot be cured until man becomes humble, and keeps himself as low as hyssop.” Cedar wood, hyssop, and scarlet were also burned with the red heifer (Numbers 19:6) and were generally used in purifications (Hebrews 9:19). Thus, the Psalmist prays, Purge me with hyssop, and I shall be clean (Psalms 51:17).