Reference for Chullin 42:9

(ויקרא א, ה) והקריבו

R'Ishmael says: 'According to the ordinance' means, according to the ordinance prescribed for the sin-offering of a bird; thus, as the nipping of the head of the sin-offering of a bird must be done close to the back of the neck, so, too' the nipping of the head of the burnt-offering of a bird must be done close to the back of the neck.<span class="x" onmousemove="('comment',' This inference is necessary, since the Law does not specify in the case of a freewill burnt-offering of a bird the place where the nipping must be done.');">⁶</span>

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