Moses instructs the Jewish people regarding how they were to conduct their conquest of the Land of Israel.
If you besiege a city...you must not destroy its fruit trees.
Our emotions are the measure of our maturity. Many people are gifted with superior intelligence or talent, but truly refined emotions are achieved by shedding childlike self-absorption and by contributing to the world.
Similarly, fruit-bearing trees provide us with nourishment and delight at their own expense, of leaving the source of their source of vitality.
In contrast, barren trees merely impress us with their stately presence; they may perhaps offer us shade, but they sacrifice nothing in doing so.
Therefore, when we seek instruction and inspiration, we should turn to people who are not only intelligent and talented, but who consistently utilize their gifts for the world's greatest good. And if course, we should emulate the example of the fruit tree ourselves.