Reference for Bava Kamma 3:6

גבי שבת תנן אבות מלאכות ארבעים חסר אחת אבות מכלל דאיכא תולדות

<b><i>GEMARA</i></b>. Seeing that PRINCIPAL CATEGORIES are specified, it must be assumed that there are derivatives. Are the latter equal in law to the former or not? Regarding Sabbath we learnt: The principal classes of prohibited acts are forty less one.<span class="x" onmousemove="('comment',' Shab. VII, 2. ');">⁸</span>

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