Reference for Yevamot 143:2

מאי טעמא איבעית אימא משום דנזופים הוו ואי בעית אימא דלא נבדור ענני כבוד

might not be scattered. R. Papa said: Hence, no circumcision may be performed on a cloudy day or on a day when the South wind<span class="x" onmousemove="('comment',' Which brings unwholesome weather. ');">⁴</span> blows; nor may one be bled<span class="x" onmousemove="('comment',' By blood-letting. ');">⁵</span>

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