This week's parsha recounts the birth of eleven of the shevatim. Leah gave birth to six of the shevatim and afterward she gave birth to a daughter whom she named Dinah. The root of the name Dinah is din (judgment) and Rashi (Bereishis 30, 21) tells us that there was a specific reason why she chose this name. Our Matriarchs knew that there would only be a total of twelve shevatim. Leah "judged" the situation and realized that if her seventh child would be a boy (and the eleventh sheivet), her sister Rochel would not give birth to more than one sheivet. Rochel wouldn't even parallel the maidservants who merited two shevatim each. Therefore, she davened to Hashem, and He switched her fetus from a boy to a girl!
Rav Wolbe (Shiurei Chumash) comments that such behavior is a demonstration of true lesheim Shamayim (for the sake of Hashem). Let us picture a darshan who preaches entirely leshem Shamayim. His sole intention and interest is the glorification of Hashem and His Torah, and he doesn't even take a penny for his work. What would happen if another darshan would arrive in town? Would he step aside and make room for another voice in town? Not allowing the second darshan to preach, would indicate that the first darshan's intentions were obviously not entirely leshem Shamayim.
Both Leah and Rochel acted entirely lesheim Shamayim. They both desperately wanted to give birth to as many shevatim as possible. Rochel sacrificed a great deal in order to procure dudaim that might enable her to have children. Leah was willing to sell the dudaim and her price showed exactly where her priorities were: Yaakov would sleep in her tent that night thereby possibly allowing her to merit yet another sheivet. Nevertheless, they were both willing to forfeit their greatest desire if it would be the cause of another person's pain. As seen in the above mentioned Rashi, Leah gave up having another boy (that she was already expecting!) when she realized that it would cause pain to her sister. Similarly, Rochel waited seven years to marry Yaakov, and in a split second decision she gave up everything and she informed Leah about the secret simanim. (She did not know then that he would end up marrying her too). Lesheim Shamayim means entirely for the sake of Hashem from beginning to end!
Each and every one of us is looking to grow in ruchniyus. However, we cannot step on someone else's toes to reach our goals. Bein Adam La'Makom cannot be achieved at the expense of Bein Adam L'Chaveiro. Our ultimate role models are the Avos and Imahos. Thus, Chazal tell us, "One is obligated to say, 'When will my actions rival the actions of our forefathers!'"