"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.