See Midrash Rabba Besraishis 22:7
וַיֹּאמֶר קַיִן אֶל הֶבֶל אָחִיו וַיְהִי בִּהְיוֹתָם וגו' (בראשית ד, ח), עַל מָה הָיוּ מִדַּיְּנִים, אָמְרוּ בּוֹאוּ וְנַחֲלֹק אֶת הָעוֹלָם, אֶחָד נָטַל הַקַּרְקָעוֹת וְאֶחָד נָטַל אֶת הַמִּטַּלְטְלִין,
“And Cain spoke to Abel his brother, and it came to pass when they were in the field…” (Genesis 4:8) What were they arguing about? They said: come let’s divide up the world, one will take the land and one will take the moveable property.
וַיֹּאמֶר קַיִן אֶל הֶבֶל אָחִיו וַיְהִי בִּהְיוֹתָם וגו' (בראשית ד, ח), עַל מָה הָיוּ מִדַּיְּנִים, אָמְרוּ בּוֹאוּ וְנַחֲלֹק אֶת הָעוֹלָם, אֶחָד נָטַל הַקַּרְקָעוֹת וְאֶחָד נָטַל אֶת הַמִּטַּלְטְלִין,
“And Cain spoke to Abel his brother, and it came to pass when they were in the field…” (Genesis 4:8) What were they arguing about? They said: come let’s divide up the world, one will take the land and one will take the moveable property.
By this division Hevel became the sole owner of all the sheep in the world.
