Leviticus 14:4 - Matthew Poole's English Annotations on the Holy Bible

Two birds; the one to represent Christ as dying for his sins, the other to represent him as rising again for his purification or justification. Clean; allowed for food and for sacrifice. Cedar wood; a stick of cedar, to which the hyssop and one of the birds was tied by the scarlet thread. Cedar seems to be chosen, to note that the leper was now freed from that putrefaction or corruption which his leprosy had brought upon him, that kind of wood being in a manner incorruptible. Scarlet; a thread of wool of a scarlet colour, Hebrews 9:19, to represent both the leper's sinfulness, Isaiah 1:18, and the blood of Christ, and the happy change of the leper's colour and complexion, which before was wan and loathsome, now sprightly and beautiful. Hyssop, chosen partly for its fragrant smell, which signified the cure of the leper's ill scent, and partly for conveniency in the use of sprinkling. See Exodus 12:22.