Reference for Bava Kamma 110:11

בור דכתיב (שמות כא, לג) כי יפתח איש בור או כי יכרה איש בור ולא יכסנו הא כסהו פטור

implying that if he covered it<span class="x" onmousemove="('comment',' Though he did not fill it with sand. ');">¹⁸</span> he would he exempt. Fire, as it is written, He that kindled the fire shall surely make restitution,<span class="x" onmousemove="('comment',' Ex. XXII, 5. ');">¹⁹</span>

Jastrow

Jastrow