For man is a tree of the field.1
Why is the fifteenth of Shevat, Rosh Hashana of the trees,2 celebrated by human beings? For "a man is a tree," not only as an idyllic metaphor, but in a very practical sense. Since Torah literally means instruction, the Scriptural comparison contains a valuable lesson for every Jew. We must endeavor to emulate the tree and its two essential characteristics: 1) a tree's sign of life is its growth, and 2) the tree's primary function is to yield fruit, which in turn become" trees and eventually bear fruit themselves. One must never be content with past achievements, but rather should constantly seek to grow, to improve and enhance his service of Gel. Moreover, he is obligated to give forth fruit, e.g. to benefit and positively influence his fellow Jews. In fact, he must affect them to the extent that they too become a source of inspiration for others ...
On his way home from Minsk after the famous disputation,3 Rabbi Schneur Zalman of Liadi stopped off in Semilian, a town renowned for its Torah scholarship, and the home of many learned men. In the course of the week that he spent there, the Rebbe attracted a quorum of ten young men and made them chassidim. All of them were scholars of high repute, known throughout the entire region. Among them was Reb Avraham Beirach of Semilian.
When Reb Avraham Beirach visited the Rebbe for the first time in Liozna and was granted a private audience, the Rebbe told him: "Man is a tree of the field. When a tree fails to produce fruit it becomes barren. One may have mastered the entire Talmud yet still be barren, Heaven forfend. A Jew must bear fruit! What good is your Torah and prayer if you have not infused light into someone else's life? The Talmud teaches: 'He who loves sages will merit to have children who are sages.' In a deeper sense, 'he who loves sages' means that he imbues a sage with the love of G-d and guides him to a new path in Divine service - such a man will surely have children who are sages."
Reb Avraham Beirach stayed in Liozna for several weeks. On his way home to Semilian he traveled through the township of Liepli, where he stayed for a short time. It was there that he began to "yield fruit". One of his first fruits was the chassid Reb Mordechai of Liepli.
Upon relating this story, Rabbi Shmuel of Lubavitch commented: "One ought to sacrifice oneself for the sake of guiding a young colleague in the ways of Chassidism, just as one is obligated to do so for the sake of rescuing the entire Jewish nation."
1. Though this phrase literally appears in the Torah as a rhetorical question (according to Rashi), in the homiletic sense it may be read as a positive statement; see Talmud, Taanis 7a.
2. Mishnah, Rosh Hashana, ch. I. The fifteenth of She vat has been designated by our Sages as being the boundary between one horticultural year and another, as far as trees are concerned. Since most of the rain of the previous year has already fallen, any growth of fruit thenceforth is a result of the blessings of the new year. Since by this time the soil is well-saturated with the rains of the previous winter, the trees newly planted after this day are assured of taking firm root and yielding fruit. A day of prayer and judgment concerning the trees and the blossoming of new fruit, it is celebrated by partaking of fruits and omitting the Vidui confession from the daily prayers.
3. See The Great Debate, p. 228.