Reference for Chullin 71:15

כי פליגי בנתקנח הדם בין סימן לסימן

[Are they not at variance, for] according to R'Simeon blood does not render foodstuffs susceptible to uncleanness and according to R'Hiyya it does? - They are nevertheless in agreement where the blood was wiped off [during the slaughtering] for according to this Master it will not render susceptible to uncleanness and so too according to the other Master.

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