Reference for Chullin 207:21

ואסור להעלות [וכו']:

AND IT IS ALSO FORBIDDEN TO PLACE etc. R'Joseph said: You can infer from this that the flesh of fowl [cooked] in milk is prohibited by the law of the Torah, for were it only [prohibited by the enactment] of the Rabbis, seeing that the actual eating thereof is [prohibited only as] a precautionary measure, would we forbid the placing [of them together upon the table] as a safeguard against the eating thereof?<span class="x" onmousemove="('comment',' This would be imposing a precautionary measure (sc. restriction of placing them together on the table) upon a precautionary measure (sc. the restriction of eating fowls cooked in milk) which is not done.');">¹⁰</span>

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