Midrasz do Kapłańska 14:5

1) (Vayikra 14:5) ("And the Cohein shall command, and he shall slaughter the one bird into an earthen vessel over living water.") "And the Cohein shall command": The commanding is by the Cohein; the slaughtering, by any man. These are the words of R. Yehudah b. R. Yossi. Rebbi says: The slaughtering, too, is by a Cohein.

2) "and he shall slaughter the one bird": the more distinctive of the two. "the one": so that one if of them dies or becomes a treifah, he takes a mate for the second one.

(Lev. 14:2:) “In the day of his cleansing.” [With what?]²⁰Lev. R. 16:7. With (according to vs. 4) “two live clean birds.” How is his offering different from all [other] offerings? It is simply that he has spoken slander. Therefore, the text says that his sacrifice is two birds, because they (like slanderers) carry their voices. (Lev. 14:4, cont.:) “And cedar wood.” In the case of the cedar, no tree is taller (gevoha) than that one; so because [the leper] has exalted (gevoha) himself like a cedar, [he has had] the leprosy come upon him.²¹PRK 4:3. Thus Simeon ben Eleazar has said, “Leprosy comes on account of haughtiness, for so you find in the case of Uzziah (in II Chron. 26:16), ‘But when he was strong, he grew so arrogant that he acted corruptly,’ and it is written (in II Chron. 26:19), ‘but during his anger with the priests, leprosy appeared on his forehead.’” (Lev. 14:4, cont.:) “And with hyssop.” Among the trees there is none [as short] as the hyssop. Because [the leper] has lowered himself, [leprosy] is therefore cured through the hyssop. (Lev. 14:5:) “[Then the priest shall give a command] to kill one bird.” Why kill one and release one? It is simply that, if he has repented, the leprosy shall not return upon him.²²Cf. Lev. 16:9. (Lev. 14:2:) “[This shall be the law of the leper in the day of his cleansing:] He shall be brought unto the priest.” What is the meaning of “He shall be brought (rt.: bw')?” He comes (rt.: bw'). Why? Because everything is far off and separated from him, for so David says (in Ps. 38:12), “My friends and companions stand aloof from my affliction, and my kinfolk stand far off.” So also it says (in Lev. 13:46), “he shall dwell alone; his dwelling shall be outside the camp,” outside the camp of Israel. It is therefore stated (in Lev. 14:2), “he shall be brought (rt.: bw'),” [meaning] he comes (rt.: bw').