Not a Free Bird
The purification procedures which brought the metzora back to the camp of Israel included the taking of two pure, identical birds, a piece of cedar wood, scarlet wool and hyssop. The Kohen would slaughter one bird in an earthenware vessel over water. The second bird would be dipped, along with the cedar wood, scarlet wool and hyssop, into the blood of the slaughtered bird, and then the blood would be sprinkled from the bird upon the metzora seven times. The bird would then fly away into an open field.
Rav Hirsch explains the symbolism of many aspects of this procedure, some of which we include below. The slaughtered bird represents the unbridled animal nature that vies to control human behavior. This nature must be subordinated to the control of human will, such that intellect and will govern action.
The remaining bird is joined together with the cedar, hyssop, and scarlet wool. The cedar and hyssop represent the highest and lowest manifestation of plant life — the entire range of flora. The scarlet wool is wool from a sheep and dyed with worm blood. Mammal (sheep) and creepy-crawler (worm) represent the entire range of fauna. All three — cedar, hyssop and scarlet wool — bound together with the red thread into one unit, represent the complete range of organic life in the field where themetzora is forced to dwell. The living bird — representing again unbridled animal instinct — is then set free to an open field.
Communal life calls upon its members to live a life of moral control over instinct. The metzora has been removed from communal life as a result of his sin. The seven sprinklings of blood signify that he who was expelled from the community must bridge the gap between unbridled animal instinct to moral freedom, by exerting all his strength, seven times over. Only when he regains the control which he previously lost is he pronounced pure and ready to rejoin the community of man.
These sprinklings are performed either on the metzora’s forehead or the back of his hand — the most human parts of the body. The hand represents action and the forehead represents thought. The process serves as a reminder that communal life of man depends on action and thought being the product of conscious free-willed choice, reminding man of his lofty calling.
§ Sources: Commentary, Vayikra 14:8