The first act took place outside the camp and restored the formerly unclean person to the fellowship of the other Israelites from whom he had experienced separation because of his skin disease. [source][source][source]
Clean animals, including clean birds, represented Israel. [1] Both of the birds used in this ritual evidently symbolized the Israelite who was about to reenter the covenant community. The bird killed probably represented the formerly unclean person whose fate was death but for God"s mercy. The bird released stood for the same person cleansed, released from the bondage of his disease, endowed with new life, and at liberty to enter the covenant fellowship again. These two birds served a symbolic function similar to that of the two goats on the Day of Atonement (ch16). [2][source]
Cedar wood had antiseptic qualities and was slow to decay, so it probably represented the continuance of life. The scarlet color of the thread looked like blood and symbolized sacrificial blood. The hyssop represented purification from the corruption of death since the priests used this spongy plant for purification in Israel"s rituals. The blood-water used to sprinkle the individual probably signified life and purification. [source][source][source]