Reference for Chullin 202:10

מאי טעמא

What is the reason [for this distinction]? - Abaye answered: The Sabbath is fixed and determined from all time, but the Day of Atonement is determined by the Beth Din.<span class="x" onmousemove="('comment',' It is therefore considered as if the Sabbath set in first, so that the prohibition of the Day of Atonement cannot be superimposed upon the existing prohibition of the Sabbath. Consequently the only prohibition that enters into consideration is that of the Sabbath, and if a person did work knowing full well that it was the Sabbath, he is not liable to bring a sin-offering, for no offering may be brought for a deliberate transgression.');">⁷</span>

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