All the members of the House of Israel are commanded concerning the sanctification of the great Name of God, as it is said, "And I will be sanctified among the children of Israel" (Lev. 22:32). And they are warned not to desecrate it, as it is said, "Neither shall ye desecrate My holy Name" (Lev. 22:32). How so? Should an idolater come and coerce an Israelite to violate any one of the commandments mentioned in the Torah under the threat that he will kill him [if he refuses]--the Israelite should transgress rather than be killed, as it is said regarding the commandments: "Which, if a person does them, he shall live by them" (Lev 18:5), meaning, live by them, and not die by them. And if he died rather than transgress, he is guilty for his loss of life.
(18) When men fight and one strikes the other with stone or fist, and he does not die but has to take to his bed— (19) if he then gets up and walks outdoors upon his staff, the attacker shall go unpunished, except that he must pay for his loss of work and make sure he is healed.
לכדתנא דבי ר' ישמעאל דתניא דבי ר' ישמעאל אומר (שמות כא, יט) ורפא ירפא מכאן שניתן רשות לרופא לרפאות
As it is taught in the school of Rabbi Yishmael, for the school of Rabbi Yishmael says: “And make sure he [the person injured] is healed” (Exodus 21:19). From here it is derived that a doctor is given permission to heal.
"A doctor is given permission to heal":
And we do not say that the merciful God wounds and He himself heals.
You shall not eat upon the blood. You shall not practice divination or interpret omens.
"Or interpret omens":
The word for omens suggests seasons and hours, for he says: “A certain day is fine for beginning a project; a certain hour is not advised for starting on a journey (Sanhedrin 66a).
[R. Yaakov Taryosh, a supercommentary on Rashi]
“A certain day is fine”:
This does not refer to the use of astrology, but rather to the Ways of the Amorites, i.e., the customs which the masses practice even though they have no good reason for them. But if one saw by way of astrology that a particular day was not good for a certain matter or project, he may avoid it, and we do not rely on miracles. And I believe that it is forbidden to go against the constellations based on [expectation of] a miracle, etc. (All this is from the responsum of Nachmanides, #283, and it is cited in Shulkhan Arukh, Yoreh Dei’ah, section 179.)
נכנסה כת ראשונה וכו׳:
איתמר אביי אמר ננעלו תנן רבא אמר נועלין תנן
מאי בינייהו איכא בינייהו למסמך אניסא אביי אמר ננעלו תנן כמה דעיילו מעלו וסמכינן אניסא רבא אמר נועלין תנן ולא סמכינן אניסא
"The first cohort would enter [the Temple in Jerusalem to prepare the Passover sacrifice]."
It is stated: Abaye said, the Mishnah teaches that the doors of the Temple closed [by themselves]. Rava said, the Mishnah teaches that they [the Levites] closed the doors.
What is the [underlying] difference between them? The difference between them is about whether we rely on a miracle. Abaye said: the Mishnah teaches that the doors of the Temple closed [by themselves]--however many wanted to enter could enter, and we rely on a miracle [to close the doors so that too many people do not enter and create danger]. Rava said: the Mishnah teaches that they [the Levites] closed the doors, and we do not rely on a miracle [to make sure the Temple did not become too crowded].
There was a boy whose father said to him, "Climb to the top of that building and bring me chicks. So he climbed to the top of the building, and sent away the mother bird [as the Torah commands] and took the young. But as he came back he fell and died. Where is "the goodness of his days," and where is "the length of his days"? Rather, the verse means, “that it may be good for you”--in the world which is completely good; and “so that your days may be long”--in the world that is completely long....
והא א"ר אלעזר שלוחי מצוה אין נזוקין התם בהליכתן שאני
והא אמר רבי אלעזר שלוחי מצוה אינן נזוקין לא בהליכתן ולא בחזירתן סולם רעוע הוה דקביע היזיקא וכל היכא דקביע היזיקא לא סמכינן אניסא דכתיב (שמואל א טז, ב) ויאמר שמואל איך אלך ושמע שאול והרגני
But didn’t Rabbi Elazar say: Those who are sent to perform a mitzvah are not harmed? There he was referring to those on their way [to perform a mitzvah], which is different.
But look, Rabbi Elazar [also] said: Those who are sent to perform a mitzvah are not harmed, either on their way or when coming back?! It was a shaky ladder [which the boy was using] where danger is known to be present; and anywhere danger is known to be present we do not rely on a miracle, as it is written, "And Samuel said, 'How can I go [to appoint David as the new king]? For Saul may hear of it and kill me!'" (I Sam 16:2).
(10) There was a famine in the land, and Abram went down to Egypt to dwell there, for the famine was heavy in the land. (11) As he was about to enter Egypt, he said to his wife Sarai, “I know what a beautiful woman you are. (12) If the Egyptians see you, and say, ‘She is his wife,’ they will kill me and let you live. (13) Please say that you are my sister, so that it may go well for me because of you, and I may remain alive thanks to you.”
(א) והיה כי יראו אתך המצרים: ....ולא סמך על הבטחת האל שהבטיחו, כי אמר שמא יגרום החטא וכן פחד יעקב אבינו אחר הבטחת האל וכן ראוי לכל צדיק שלא יסמוך במקום סכנה על הנס וישמור עצמו בכל תחבולה אשר יוכל, ועל זה אמר שלמה אשרי אדם מפחד תמיד (משלי כ״ח:י״ד) וכן אחז"ל (תענית ט') מניין שאין סומכים על הנס שנאמר לא תנסו את ה' אלהיכם (דברים ו') וכן ראינו שמואל הנביא כשהלך בשליחות האל ופחד משאול, ואמר "ושמע שאול והרגוני" (שמואל א' ט"ז) וגם האל שבח פחדו ולא אמר לו אל תפחד כי לא יהרגך, אבל אמר לו "עגלת בקר תקח בידך" והודה לו כי טובה היתה מחשבתו שהיה מפחד, וכן ראוי לכל צדיק שיעשה כן ולא יבטח על הנס.
"If the Egyptians see you":
....And Abraham did not rely on the assurance of God's promise to him, for he said [to himself]: 'Maybe I have sinned and that changes things.' And so too we find that our father Jacob was [still] afraid after God's promise. And so too it is proper for every righteous person not to rely on a miracle in a situation of danger, but he should protect himself using any means he can. And regarding this Solomon said, "Happy is the man who is always afraid" (Proverbs 28:14).
And so too our Sages of blessed memory said: From where do we learn that we do not rely on a miracle? As it is stated, "Do not test the Lord your God" (Deut 6:16).
And so too we see that when Samuel the prophet went on God's mission he was afraid of Saul and said, "For Saul may hear of it and kill me!" (I Sam 16:2). And God also approved of his fear and did not tell him, 'Do not be afraid for he shall not kill you,' rather he told him, "Take a calf along with you [and you shall say, 'I have come to sacrifice to the Lord']" (ibid.), thus acknowledging that his attitude of fear was good. And so too it is appropriate for every righteous person to act this way and not trust in a miracle.