Is An Issur Mafkia Zman?

There is a discussion in the achronim that explores the following question: Does a prohibition מפקיע [neutralize] time? In other words, if there is an act that has a set time for its performance but during part of the time it is forbidden to do this action, do we view this forbidden time period as if it is not part of the time at all or do we say זמן לחוד ואיסור לחוד, the time is one issue while the איסור is a separate issue?

The acharonim bring numerous proofs, f'rinstence: It says [Psachim 5a] "זמן שחיטה אמר רחמנא" - meaning, that from midday on the 14th of nissan it is considered the time of bringing the korban pesach even though it is אסור to bring the korban until the korban tomid is brought. We see then that the איסור is NOT מפקיע time.

Of course, this is not a proof, because bringing the tomid first is not מעכב and if one brings the pesach first he is yotzei בדיעבד. So all we can learn is that with respect to time we look at the בדיעבד  and not לכתחילה.  

Another proof is from the machlokes [Sanhedrin 13a] is the first day of succos must occur in the fall, as the pasuk says   חג האסיף תקופת השנה [the holiday of gathering at the season of the year], does this mean that ALL of succos has to occur during the new תקופה [season] or is it enough if just chol hamoed is during the new season [this question will determine if me must make it a leap year]. The machlokes is on the words חג האסיף the holiday of gathering. According to the latter opinion, since in practice one may only gather on chol hamoed, that is when there must be a new season. The gemara asks on the opinion that even the first day of yom tov must occur during the new תקופה that the pasuk implies that it must be a time of gathering, which is only during chol hamoed. The gemara answers: חג הבא בזמן אסיפה - a holiday that occurs during the period of gathering [but not that one must actually be able to gather]. Apparently, the machlokes is if the איסור is מפקיע the זמן. According to the first opinion, even though there is an איסור against gathering during yom tov, this איסור isn't מפקיע the זמן and it is still called זמן האסיף. According to the latter opinion, the איסור is מפקיע the זמן and therefore the first day of yom tov need not be in the new תקופה because it is not זמן האסיף.

However, that is not an absolute proof, because the question there is not whether the time per se is neutralized but on the act of gathering. The machlokes is if the Torah is referring to the time of gathering which is even during the first day or on the act of gathering, which is only on chol hamoed.

There is more.....:-)

Li'ilui nishmas Elisha Chanina ben HaRav Aharon Avraham.

[עפ"י המדות לחקר ההלכה ח"ב עמ' של"ד]