Musar על קהלת יב:ה

As to Solomon's using the word "vineyard," aside from the fact that all of Israel is considered a vineyard, viz. (Isaiah 5:7): "For the vineyard of the L-rd of hosts is the house of Israel," and every Jew has a portion in this vineyard— aside from this, everyone has a distinct vineyard in Gan Eden, as it is written (Koheleth 12:5): "A man goes to his eternal house." And he must take especial care with it, to plant it with pleasing growths and to guard it that it not spoil.