Mishnah 7:1. In this chapter, we move on to discuss the invalidations of bird offerings. The first two Mishnayos repeat, to a certain extent, principles that were already explained earlier, and the Mishnah before us deals with the bird chatas.
Three conditions are required for the validity of a bird chatas:
Proper melikah - Severing only one siman, without removing the head, and anywhere in the azarah.
Application of the blood - Which includes the sprinkling and the squeezing out, specifically on the yesod (base) below the red line, and generally at the southwestern corner.
Proper intention - That the service be performed for the sake of a chatas.
When these three conditions are met - the offering is valid; and in the absence of any one of them - the offering is invalid.
The words of the Mishnah:
"Chatas ha'of she'asah lematah kema'aseh chatas leshem chatas - kesherah" - The blood was applied below, in its proper place, the act of melikah was done according to the law of a chatas, and the intention was for the sake of a chatas. There is no novelty in this, but rather the Mishnah begins with it for the sake of the parallel structure that will follow.
And from here to the cases of invalidation:
"Kema'aseh chatas leshem olah" - The procedures of the chatas were done properly, but the intention was mistaken, for the sake of an olah.
"Kema'aseh olah leshem chatas" - The procedure was done not according to the law of the chatas, but in the manner of an olah, even though the intention was for the sake of a chatas.
"Kema'aseh olah leshem olah" - The procedure was done in the manner of an olah: two simanim, removing the head and applying the blood above the line, and the intention was also for the sake of an olah. It is certainly invalid.
"Asah lema'lah kema'aseh kulam - pesulah" - Even if everything was done properly, and only the blood was applied above the line instead of below it, this law is no different from the other invalidations, and the offering is invalid.
In summary: A bird chatas is valid only when done below, according to the procedure of a chatas, and for the sake of a chatas. A change in the procedure, a change in intention, or applying the blood above - any one of these invalidates the offering. We will return to the parallel between the cases later on.