Eruvin 54a: Divrei Torah are compared to a fig tree. (The figs ripen at different times.) Whenever one feels around, he finds figs. Likewise, whenever one ponders Divrei Torah, he finds Ta'am (taste, i.e. understanding).

Rashi: He eats the fruits of his deeds.

Malbim: One who wants to eat the Peros of a fig tree, he must guard it. Netzirah is more than Shemirah. Figs ripen one at a time. He must gather every morning, before the sun shines. If not, those that ripened will get wormy (Midrash, Yerushalmi).

Malbim, partially from Bamidbar Rabah 12:9: One who guards his master must be found by him every morning, and gather the fruits of his Chachmah. This refers to Yehoshua, who served Moshe day and night - "Lo Yamush mi'Toch ha'Ohel" (Shemos 33:11). He merited honor - Moshe leaned his hands on him.