(Devarim 19:5) "And one who comes with his neighbor in the forest": Just as a forest is a place that the slain and the slayer were permitted to enter, so all such places (are subsumed in the halachah) — to exclude the owner's courtyard, which the slayer had no right to enter.
"to chop wood": Abba Shaul says: Just as the chopping of wood is a (merely) "permitted" activity, so, all such activities are subsumed (in the halachah) — to exclude (a mitzvah activity, such as) a father beating his son (to chastise him), etc.
(דברים יט ה) וַאֲשֶׁר יָבֹא אֶת רֵעֵהוּ בַּיַּעַר, מָה יַּעַר, רְשׁוּת לַנִּזָּק וְלַמַּזִּיק לִכָּנֵס שָׁם – אַף כָּל שֶׁהוּא רְשׁוּת לַנִּזָּק וְלַמַּזִּיק לִכָּנֵס לְשָׁם. יָצָאת חֲצַר שֶׁל בַּעַל הַבַּיִת שֶׁאֵין רְשׁוּת לַנִּזָּק וְלַמַּזִּיק לִכָּנֵס שָׁם.
(Devarim 19:5) "And one who comes with his neighbor in the forest": Just as a forest is a place that the slain and the slayer were permitted to enter, so all such places (are subsumed in the halachah) — to exclude the owner's courtyard, which the slayer had no right to enter.
לַחְטֹב עֵצִים, אַבָּה שָׁאוּל אוֹמֵר: מַה חֲטִיבַת עֵצִים רְשׁוּת – אַף כָּל שֶׁהוּא רְשׁוּת, יָצָא הָאָב הַמַּכֶּה אֶת בְּנוֹ, וְהָרַב הָרוֹדֶה אֶת תַּלְמִידוֹ, וּשְׁלִיחַ בֵּית דִּין.
"to chop wood": Abba Shaul says: Just as the chopping of wood is a (merely) "permitted" activity, so, all such activities are subsumed (in the halachah) — to exclude (a mitzvah activity, such as) a father beating his son (to chastise him), etc.