As for the living bird, he shall take it,.... And dispose of it as after directed; for there was an use for that:

and the cedar wood, and the scarlet, and the hyssop; which were all bound up in one bundle, but whether the living bird was joined to them is a question; according to Jarchi they were separate, the bird by itself, and the cedar wood, &c. by themselves; they were neither bound together nor dipped together; and Ben Gersom is very distinct and expressive; we learn from hence, says he, that three were bound up in one bundle, but the living bird was not comprehended in that bundle; but according to the Misnah (c) they were all joined together, for there it is said, he (the priest) takes the cedar wood, scarlet, and hyssop, and rolls them up with the rest of the scarlet thread, and joins to them the extreme parts of the wings and of the tail of the second bird and dips them; and this seems best to agree with the text, as follows:

and shall dip them and the living bird in the blood of the bird that was killed over the running water; that is, into the blood of it as mixed with the running water in the earthen vessel, which together made a sufficient quantity for all these to be dipped into it; whether separately, first the living bird, and then the cedar wood, and scarlet, and hyssop, or all together: the bird that was kept alive was a type of Christ, who as a divine Person always alive, and ever will; he is the living God, and impassable: the dipping of this living bird in the blood of the slain one denotes the union of the two natures in Christ, divine and human, and which union remained at the death of Christ; and also shows that the virtue of Christ's blood arises from his being the living God: the dipping of the cedar wood, scarlet, and hyssop, into the same blood, signifies the exercise of the several graces of the Spirit upon Christ, as crucified and slain, and their dealing with his blood for pardon and cleansing, as faith and hope do, and from whence love receives fresh ardour and rigour.

(c) Ebr. Concord. part. 64. No. 318. & Bartenora in ib.

As for the living bird, he shall take it, and the cedar wood, and the scarlet, and the hyssop, and shall dip them and the living bird in the blood of the bird that was killed over the running water:

14:1-9 The priests could not cleanse the lepers; but when the Lord removed the plague, various rules were to be observed in admitting them again to the ordinances of God, and the society of his people. They represent many duties and exercises of truly repenting sinners, and the duties of ministers respecting them. If we apply this to the spiritual leprosy of sin, it intimates that when we withdraw from those who walk disorderly, we must not count them as enemies, but admonish them as brethren. And also that when God by his grace has brought to repentance, they ought with tenderness and joy, and sincere affection, to be received again. Care should always be taken that sinners may not be encouraged, nor penitents discouraged. If it were found that the leprosy was healed, the priest must declare it with the particular solemnities here described. The two birds, one killed, and the other dipped in the blood of the bird that was killed, and then let loose, may signify Christ shedding his blood for sinners, and rising and ascending into heaven. The priest having pronounced the leper clean from the disease, he must make himself clean from all remains of it. Thus those who have comfort of the remission of their sins, must with care and caution cleanse themselves from sins; for every one that has this hope in him, will be concerned to purify himself.