Vayera - Why did Yitzchak carry the wood but not the knife?

The passuk in this week’s sedrah says:

וַיִּקַּח אַבְרָהָם אֶת-עֲצֵי הָעֹלָה וַיָּשֶׂם עַל-יִצְחָק בְּנוֹ וַיִּקַּח בְּיָדוֹ אֶת-הָאֵשׁ וְאֶת-הַמַּאֲכֶלֶת

“And Avraham took the wood for the olah and he placed it on his son Yitzchak and he took in his hand the flint and the knife.”

The Tzaphnas Paneach asks, why did Avraham put the wood on Yitzchak but not the flint and the knife? He answers that as Yitzchak was a korban, it would have been assur for Avraham to ask him to carry the knife.

The Tzaphnas Paneach proves that this is the halacha from a gemara in Pesachim (דף ס״ו עמוד א') that relates that erev Pesach once fell on Shabbat and the nesiim in Yerushalayim did not know if it was mutar to bring the korban pesach on Shabbos. Hillel proved from a passuk that they could bring the korban.

The nesiim then asked Hillel what the halacha is concerning someone who forgot to bring the shechita knife for the korban to the beis hamikdash before Shabbat, as they couldn’t carry it to the beis hamikdash on Shabbat.

Hillel said:

הנח להן לישראל אם אין נביאים הן בני נביאים הן

[I do not know but] leave [it to] the people – if they are not neviim they are the sons of neviim (i.e. they will know themselves what to do.)

The Gemara relates:

למחר מי שפסחו טלה תוחב לו בצמרו גדי תוחב לו בין קרניו

The next day, someone whose korban pesach was a sheep put the knife in its wool, if their korban pesach was a goat they put the knife between its horns. (That is, they let the korban pesach carry the knife.)

The gemara asks, how could they let the korban carry the knife?

והא קא עביד עבודה בקדשים?

He is doing work with a korban? (If someone uses a korban for their own personal use then this is meilah (misappropriation).)

The gemara answers:

כהלל, דתניא אמרו עליו על הלל מימיו לא מעל אדם בעולתו אלא מביאה חולין לעזרה ומקדישה

They did like Hillel – as we have learnt in a beraisah – they said about Hillel, no-one was ever moel in his korban because he would bring it to the beis hamikdash before he was makdish it and he would make it into a korban only once he reached the beis hamikdash.

You see from this gemara that it assur to make a korban carry a knife, even if this is the knife that will be used to shecht it. We can understand therefore why Avraham did not ask Yitzchak, who was a korban, to carry the knife.

However it is evident from the Yerushalmi in Pesachim (פרק ו הלכה א) that the Yerushalmi argues with the Bavli and is of the opinion that the people at the time of Hillel were allowed to use the korban pesach to carry the knife since the knife is used for making the korban.

The Yerushalmi brings a mishnah in Parah (2:3) which says:

קושרה במוסירה עשה לה סנדל בשביל שלא תחליק פרש טליתו עליה מפני הזבובין כשרה.

[If a person did work with a Parah Adumah then it is passul, however if the Parah Adumah was made to do something which was for its own benefit such as] he tied it with a harness or made sandals for it so that it should not slip or if he spread his tallis over it to protect it from flies it is kosher.

The Yerushalmi also says that we can see from the fact that the korban pesach was used to carry the knife that a Parah Adumah can also carry its own knife: 

 …שאם תלה בה סכין לשוחטה כשרה

If he hung a knife on it in order to slaughter it it is kosher.

We see from the comparison of korban pesach to parah adumah that the Yerushalmi understands that the korban pesach  (and any other korban) may carry its own knife even after it has become a korban. It is therefore be difficult to understand according to this opinion why Yitzchak did not carry the knife as well as the wood.

The Tzafnas Paneach answers as follows:
Tosafos proves that the halacha is that the knife used to slaughter a korban does not need to be a kli sha'res.

The mishna says in Ezehu Mekoman:

אֵיזֶהוּ מְקוֹמָן שֶׁל זְבָחִים ? קָדְשֵׁי קָדָשִׁים - שְׁחִיטָתָן בַּצָּפוֹן. פָּר וְשָׂעִיר שֶׁל יוֹם הַכִּפּוּרִים: שְׁחִיטָתָן בַּצָּפוֹן, וְקִבּוּל דָּמָן בִּכְלִי שָׁרֵת בַּצָּפוֹן.

Where do you slaughter korbanos? קָדְשֵׁי קָדָשִׁים are slaughtered in the north of the mizbeach as are the פָּר וְשָׂעִיר of Yom Kippur. They are slaughtered in the north and their blood is accepted in a kli sha'res in the north. (That is, the bowl that is used to accept the blood of the korban must be a kli sha'res.)

Tosafos infers from the fact that the mishna says that the bowl used to accept the blood must be a kli sha'res but does not discuss the knife, that the knife is not a kli sha'res.

The Tzaphnas Paneach explains that the Yerushalmi that says that the korban can carry the knife is of the opinion that the knife must be a kli sha'res, however since we hold le’halachah like tosafos, that the knife does not need to be a kli sha'res, the korban would not be allowed to carry it.

Therefore Avraham did not give the knife to Yitzchak to carry but he did give Yitzchak the wood, because the wood used for burning korbanos is hekdesh and therefore can be carried by the korban.

Why according to the Yerushalmi may the korban only carry the knife if it is a kli sha'res?
It would appear that according to the Tzaphnas Paneach the Yerushalmi opines that if the knife is hekdesh and has an obvious purpose for the korban then the korban may carry the knife as it is evident that the knife will be used for the korban.

However if the knife is chullin, since there is no evidence when the korban carries the knife that the knife will be used for the korban then even the Yerushalmi agrees that it is meilah for the korban to carry the knife because currently this is for the benefit of the owner even though the owner may later choose to use the knife for the shechitah.