“This shall be the law…” (Vayikra 14:2)
The Gemara (Arachin 16a) lists several reasons why one would contract the disease of tzaraas (often translated as leprosy). The list almost exclusively mentions Mitzvos affecting other people rather than those which deal only with Hashem, and they each share one common denominator – causing harm to a fellow Jew.
One may think that if he is not speaking lashon hara about someone or if he is not jealous over his friend’s success then he is acting in accordance with what Hashem wants from him. While it is true that Hashem forbids lashon hara and other forms of hurting people, nevertheless, merely refraining from or avoiding these feelings is not enough. We must actively look for the good in people and see how we can improve their lives in a good and positive way. This is one of the “fundamental paths of kindness” according to Rabbeinu Yona, who stresses that everyone must think of good advice that can benefit his fellow and make his life better. (Shaarei Teshuva 3:54)
One person who exemplified this precept was Rav Nosson Tzvi Finkel zt”l, the Rosh Yeshiva of the Mir Yeshiva, who suffered from Parkinson’s disease. He related that at the times when he had absolutely no energy to learn he would just lie down and spend time thinking of different ways to encourage others in their learning. (Rav Moshe Kormornick Shlita)