Yevamot — Daf 6a

לאו דמחמר ואפי' הכי לא דחי

אלא דקיימא לן דאתי עשה ודחי לא תעשה ליגמר מהכא דלא לידחי

וכ"ת שאני לאוי דשבת דחמירי והא תנא בעלמא קאי ולא קפריך

דתניא יכול אמר לו אביו היטמא או שאמר לו אל תחזיר יכול ישמע לו ת"ל (ויקרא יט, ג) איש אמו ואביו תיראו ואת שבתותי תשמורו כולכם חייבין בכבודי

אלא משום דאיכא למיפרך

מה להנך שכן הכשר מצוה

אלא סד"א תיתי מבנין בית המקדש דתניא יכול יהא בנין בית המקדש דוחה שבת ת"ל (ויקרא יט, ל) את שבתותי תשמורו ומקדשי תיראו כולכם חייבין בכבודי

מאי לאו בבונה וסותר וטעמא דכתב רחמנא את שבתותי תשמורו הא לאו הכי דחי

לא לאו דמחמר ואפילו הכי לא דחי ואלא דקיימא לן דאתי עשה ודחי ל"ת ליגמר מהכא דלא דחי

וכ"ת שאני לאוי דשבת דחמירי והא תנא בעלמא קאי ולא קא פריך דתניא יכול אמר לו אביו היטמא או שאמר לו אל תחזיר יכול ישמע לו תלמוד לומר איש אמו ואביו תיראו וגו' כולכם חייבים בכבודי

אלא משום דאיכא למיפרך מה להנך שכן הכשר מצוה הכשר מצוה תיפוק לי מהתם

אין הכי נמי ואת שבתותי תשמורו ומקדשי תיראו למה לי מיבעי ליה לכדתניא יכול יתיירא אדם ממקדש תלמוד לומר את שבתותי תשמורו ואת מקדשי תיראו נאמרה שמירה בשבת ונאמרה מורא במקדש מה שמירה האמורה בשבת

this is a case  of ass driving.  And [you say that] it does not supersede  even in such a case?  But then what of the generally accepted rule that a positive precept supersedes a prohibition. Should it not be inferred from this case that it does not supersede!  And if it be replied that the prohibitions of the Sabbath are different  because they are more stringent,  surely the following Tanna, [it may be pointed out,] speaks of prohibitions generally  yet no one advances any objection.  For it was taught: Since it might have been assumed that if his father had said to him,  'Defile yourself',  or if he said to him, 'Do not restore,'  he must obey him, it was explicitly stated, Ye shall fear every man his mother, and his father, and ye shall keep my Sabbaths,  it is the duty of all of you to honour Me!  — The real reason  is because this objection may be advanced: Those  are in a different category  since they are also essentials in the execution of the precept. But [the reason  is because] it might have been assumed that this  should be derived from the precept of the building of the Sanctuary. For it was taught: Since it might have been assumed that the building of the Sanctuary should supersede the Sabbath, it was explicitly stated, Ye shall keep My Sabbaths, and reverence My Sanctuary;  it is the duty of all of you to honour Me. Now is not the case in point one of [a father's order to his son to] build or to demolish,  and yet the reason [why it does not supersede the Sabbath is] because the All Merciful has written, 'Ye shall keep My Sabbaths',  but had that not been written it would have superseded?  — No; the case in point is one of ass driving. And [you say] that it  does not supersede a prohibition even in such a case?  But what of the generally accepted rule that a positive precept supersedes a prohibition? Should we not infer from this case that it does not supersede! And if it be replied that the prohibitions of the Sabbath are different  because they are of a more stringent nature,  surely the following Tanna [it may be pointed out] speaks of prohibitions generally  yet no one advances any refutation.  For it was taught: Since it might have been assumed that if his father had said to him,  'Defile yourself',  or if he said to him, 'Do not restore,'  he must obey him, hence it was explicitly stated, Ye shall fear every man his mother, and his father etc.,  it is the duty of all of you to honour Me!  — The true reason  is because this objection may be advanced: Those  are in a different category  since they are also essentials in the execution of the precept.  [But the law relating to] essentials in the execution of a precept could be derived from the previously cited text!  — That is so indeed. What need, then, was there for the text, Ye shall keep My Sabbaths, and reverence My Sanctuary?  — It is required for the following deduction:  As it might have been imagined that a man should reverence the Sanctuary, it was explicitly stated in the Scriptures, Ye shall keep My Sabbaths, and reverence My Sanctuary;  the expression of 'keeping' was used in relation to the Sabbath and [in the same verse] that of 'reverence' in relation to the Sanctuary [in order that the following comparison may be made]: As in the case of 'keeping' used in relation to the Sabbath