Reference for Pesachim 4:1
הא מדקאמר ובלילה יהי כגנב אלמא אור יממא הוא התם הכי קאמר אי פשיטא לך מילתא כנהורא דאנפשות קאתי רוצח הוא וניתן להצילו בנפשו ואי מספקא לך מילתא כליליא יהי בעיניך כגנב ולא ניתן להצילו בנפשו
Now since he states, 'and in the night he is as a thief,' it follows that 'or' is day? - The meaning there is th if the matter is as clear as light to you that he [the thief] comes [even] to take life, he is a murderer, and h [the victim] may be saved at the cost of his [the thief's] life; but if you are doubtful about it, like [the darkness of] the night, you must regard him [only] as a thief, and he [the victim] must not be saved at the cost of his life.<span class="x" onmousemove="('comment',' V. Ex. XXII, 1; the present verse lays down the conditions for the law stated there to be applicable.');"><sup>1</sup></span> An objection is raised: Let the stars of the twilight thereof be dark: let him look for light [or], but have none; neither let it behold the eyelids of the morning.<span class="x" onmousemove="('comment',' Job. III, 9.');"><sup>2</sup></span>