Reference for Bava Kamma 99:4
ורב יוסף אמר בבור ברה"י כולי עלמא לא פליגי דמחייב מאי טעמא בעל הבור אמר רחמנא בבור דאית ליה בעלים עסקינן
And R. Akiba? [He might reply that] both terms<span class="x" onmousemove="('comment',' Of opening and of digging. ');"><sup>7</sup></span> required to be explicitly mentioned. For if the Divine Law had said only 'If a man open' it might perhaps have been said that it was only in the case of opening that covering up would suffice [as a precaution], whereas in the case of digging covering up would not suffice, unless the pit was also filled up. If [on the other hand] the Divine Law had said only If a man dig it might have been said that it was only where he dug it that he ought to cover it, as he actually made the pit, whereas where he merely opened it, in which case he did not actually make the pit, it might have been thought that he was not bound even to cover it. Hence it was necessary to tell us [that this was not the case but that the two actions are on a par in all respects]. But what then did R. Ishmael mean by saying, [If a man digs a pit in private ground and opens it on to a public place, he comes liable] and this is the Pit of which the Torah<span class="x" onmousemove="('comment',' V. p. 284, n. 3. ');"><sup>8</sup></span>