Midrash for Pesachim 129:12

והאמר ר' אלעזר מודה ר' יהודה לענין כפרה שאינו מכפר שנא' (ויקרא יז, יא) כי הדם הוא בנפש יכפר

The priests are careful. If they ar careful, why was it spilled? - Because of the speed with which they work,<span class="x" onmousemove="('comment',' Zariz denotes both careful and speedy; they hurried to catch the blood, present it at the altar, and sprinkle it.');">¹³</span> it is spilled. But the draining blood<span class="x" onmousemove="('comment',' Tamzith denotes the last blood which slowly drains off the animal, contrad. to the lifeblood, which gushes forth in a stream.');">¹⁴</span> is mixed with it?<span class="x" onmousemove="('comment',' Whereas the 'life-blood' is required for sprinkling.');">¹⁵</span> - R'Judah is consistent with his view, for he maintained, The draining blood is [considered] proper blood. For it was taught: The draining blood is subject to a 'warning';<span class="x" onmousemove="('comment',' This is a technical designation for a negative injunction whose violation is punished by lashes. But it involves no kareth, as does the consuming of the life-blood (v. Lev. XVII, 10f) .');">¹⁶</span> R'Judah said: It is subject to kareth.<span class="x" onmousemove="('comment',' Just like life-blood. Hence it is also the same in respect to sprinkling.');">¹⁷</span> But surely R'Eleazar said, R'Judah agrees in respect to atonement, that it does not make atonement, because it is said, for it is the blood that maketh atonement by reason of life:<span class="x" onmousemove="('comment',' Ibid.');">¹⁸</span>

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