כִּי אִם בְּתוֹרַת ה' חֶפְצוֹ, וּבְתוֹרָתוֹ יֶהֶגֶּה יוֹמָם וָלָיְלָה. וְהָיָה כְּעֵץ שָׁתוּל עַל פַּלְגֵי מָיִם; אֲשֶׁר פִּרְיוֹ יִתֵּן בְּעִתּוֹ, וְעָלֵהוּ לֺא יִבּוֹל, וְכֺל אֲשֶׁר יַעֲשֶׂה יַצְלִיחַ
"(Rather in the Torah of Hashem is his desire, and in His Torah he meditates day and night.) He shall be like a tree deeply rooted alongside brooks of water, that yields its fruit in its season, and whose leaf never withers; and everything that he does will succeed." (Tehillim 1:2,3)
R' Hirsch comments on the phrase "פַּלְגֵי מָיִם", or "brooks of water," that the word "פַּלְגֵי" denotes many brooks streaming from one common source. He says that the same holds true by the Torah. The Torah saturates those who learn it in all aspects of life, making their lives fruitful.