Musar for Sanhedrin 7:6

לאחר שיצאו יצא ומחזיר אחריהם אמר להן אי אתם זקוקים לכך שבועיים קרינן ויש אם למקרא

[denoting one application]. In the case of a sin offering, however, they hold that two applications are required; but the Hillelites hold that in the case of a sin offering also a single sprinkling effects atonement. And R. Huna said: What is the Shammaites' reason for their opinion? — It is that the plural 'karnoth' [horns of the altar] occurs three times in this context<span class="x" onmousemove="('comment',' Lev. IV, 25, 30, 34. ');">⁸</span> denoting six, and so implying that four sprinklings are prescribed in the first instance, but that two are indispensable. But the Hillelites argue that since '<i>karnoth</i>'^{<span class="x" onmousemove="('comment',' Following the Mikra. ');">⁹</span>}

Shenei Luchot HaBerit