רַבִּי שִׁמְעוֹן אוֹמֵר, הַמְהַלֵּךְ בַּדֶּרֶךְ וְשׁוֹנֶה, וּמַפְסִיק מִמִּשְׁנָתוֹ וְאוֹמֵר, מַה נָּאֶה אִילָן זֶה וּמַה נָּאֶה נִיר זֶה, מַעֲלֶה עָלָיו הַכָּתוּב כְּאִלּוּ מִתְחַיֵּב בְּנַפְשׁוֹ:
Rabbi Shimon said: One who is walking down a path, and is studying, and breaks off from their study and says, “How lovely is this tree!,” or “How lovely is this hill!” scripture considers it as if they had forfeited their life.
המהלך בדרך יחידי ושונה ומפסיק ממשנתו כו' (אבות ג, ד).
קשה דהל"ל ומפסיק ממשנתו והוה ידענין דהיה שונה.
עוד קשה מעלה עליו הכתוב ולא מפרש איזה כתוב.
וי"ל הפי' כי ההולך בדרך הישר ואפי' הוא יחידי שאינו דבוק בהש"י
ושונה ומפסיק ממשנתו ר"ל מפסיק א"ע מהש"י מחמת משנתו דהיינו שבא לו גדלות והתפארות מחמת משנתו שסובר שהוא משנתו שלו
ואומר מה נאה אילן זה ועל עצמו אומר כן בלבו כמ"ש כי האדם עץ השדה ואומר דהוא אלנא די רבא ותקיף
ומה נאה ניר זה כמ"ש נירו לכם ניר פי' שאומר שמכין לעצמו חלק לעה"ב ע"י משנתו
מעלה עליו הכתוב פי' כתוב שנ' תמים תהי' עם ה' אלהיך פי' אפי' כשתעסוק בתורה שנאמר בה תורת ה' תמימה וז"ש תמים תהיה אפי' בעסק התורה תהי' עם ה' אלהיך ולא תאמר הלא התורה ממילא נקרא תורת ה'
וז"ש מעלה עליו הכתוב הזה שכולל כל התורה כאלו מתחייב בנפשו:
"One who walks alone down a path, and is studying, and breaks off from their study..." (Pirkei Avot 3:4 [in Sefaria's version, Avot 3:7]).
There is a difficulty here. For it ought to have just said, "breaks off from their study" and we would have known they were "studying."
And what's more, it says "scripture considers it [as though they were liable for death]," but it doesn't explain which verse!
And it's possible to explain this as follows:
"one who walks down a path" - is the one who walks down the straight path -- but even so they are "alone," which is to say that they are not attached to God.
"and is studying, and breaks off from their study", that is to say: they break themselves off from God because of their study. Because greatness and glory come to them because of their study, and they come to think that this is their own doing.
"They say 'how lovely is this tree!'" -- they say this referring to themselves, as it is written "for is a person a tree of the field" (Deuteronomy 20:19). And they also say that "this tree has grown and become mighty" (Daniel 4:17) [c.f. use of the verse in Zohar 3:53b in reference to tree of life/Torah].
"How lovely is this hill!" -- as it is written "Pile up a hill..." (Jeremiah 4:3). Meaning, that they say they are preparing for themself a portion in the World to Come by means of their study.
"Scripture considers them..." -- meaning, scripture like, "You shall be wholehearted with the Lord your God." (Deuteronomy 18:13) -- meaning, even when you are engaged with Torah! As it says of Torah, "the Torah of God is whole" (Psalms 19:8) -- so when it says "You shall be wholehearted" -- that means even when you engage with Torah, you should be "with the Lord your God." So do not say, "Isn't the Torah itself called 'Torah of God'?" [and that this suffices for one's relationship with God].
And that is why it says "scripture considers it" -- that includes all the Torah, "as if they had forfeited" it with their own life/self.
רַבִּי חֲנִינָא בֶן חֲכִינַאי אוֹמֵר, הַנֵּעוֹר בַּלַּיְלָה וְהַמְהַלֵּךְ בַּדֶּרֶךְ יְחִידִי וְהַמְפַנֶּה לִבּוֹ לְבַטָּלָה, הֲרֵי זֶה מִתְחַיֵּב בְּנַפְשׁוֹ:
Rabbi Haninah ben Hakhinai said: one who stays awake at night, or walks on the way alone, or turns one's heart to idle matters - behold, this one has forfeited their life.