Rabbi Aba, Rabbi Yehudah and Rabbi Yitzchak came to visit Rabbi Yossi that was sick. They saw him fall on his face and sleeping. They sat and waited until he woke up with a smiling face. Rabbi Yossi told them about a new thing he saw when his soul ascended during his sleep. He saw those who dedicated their lives to their holy master going into thirteen rivers of pure persimmon (אֲפַרְסְמוֹן, Balsam) oil and the Holy One Blessed be He, have fun with them. In addition Rabbi Yossi saw things that he was not allowed to reveal. He explained that because of all the things his soul saw, his face was smiling.
Rabbi Aba praised Rabbi Yossi for his merits and quoted Isaiah 64:3
עַיִן לֹא רָאָתָה אֱלֹהִים זוּלָתְךָ יַעֲשֶׂה לִמְחַכֵּה לוֹ.”
“No eye has seen God besides You, who will act on behalf of those who wait for Him.”
The thirteen rivers of (אֲפַרְסְמוֹן) Persimmon (Balsam) oil are aspects of Light of Chassadim that comes from the highest level of Keter. It’s a result of the love unification of Zeir Anpin and Malchut.
Tzadikim that dedicate their lives for the love of God and follow his ways, have merits to enjoy the supernal Chassadim (מים רבים) that flows like rivers of pure Balsam oil.