"Hashem saw the earth and it was corrupted for all flesh had debased its way" (Bereishis 6:12).

Rashi quotes the Midrash that not only was man corrupt, even the animals mated with animals of other species, which is considered by Torah a depravity. Furthermore, the actual earth was corrupt: if, for instance, one planted wheat, barley would grow. The Meforshim ask how is it possible for animals to become corrupt when they do not have an evil inclination? More difficult to understand is how can the earth be corrupt, since it's not a living being?

Rabbi E. Lopion zt'l tells of when he was a bochur studying in Lomza, there was a great old hospital where patients would leave the hospital more ill than when they were admitted. The doctors couldn't figure out why. It was finally determined that the hospital being so old, its walls had absorbed diseases and bacteria, and it had to be destroyed. The lesson from this story is that just as there is physical bacteria, so too there is spiritual "bacteria", the impurity caused by sin. This spiritual pollution has a deleterious effect on others even if they had no part of the sin, and even if they didn't see the sin being committed. Just being in the vicinity of evil can ruin someone. At the time of the flood, the people in Noach's generation were so corrupt that literally the whole world was infected, even the animals and earth. The only thing to be done was to destroy everything and start again.

The Gemorah says that after a person dies, the walls and beams of his house testify about him. Our actions affect our very homes, even though we can't physically assess it.The Mishnah (Negaim 12:6) speaks of someone living in a semi-detached home who spoke lashan hora and had the intervening wall afflicted with leprosy. Halacha states that both sides of the afflicted wall must come down. Even though the neighbor is free of sin, still the very wall has become infected, and since he shares an infected wall, he must remove it. Based on this, Rav Lopion concludes that when buying a home, one should make sure that the previous owner was not wicked, for if he was, his actions have left impressions on the house and in turn could effect the new owner. Beis Halevi asserts that even if someone has inborn character traits that give him strength in a certain area, he can still be negatively affected, to the point where he'll develop a second nature prone to sin.

Rabbi Tzvi Belsky used to live in Memphis, Tennessee. One room in his home was set aside for his study, where he would spend hours immersed in Torah study. Eventually, he left town and sold his house to a non- observant Jewish artist. Coming back for a visit, he met the artist who was now religious. The artist explained how he came to religion. "Since I moved into your home, I found that I was constantly painting Jewish and Biblical themes. A Rabbi told me that maybe it was time to learn about my roots, and slowly but surely I became religious". Rabbi Belsky asked to be shown the room which was the artist's studio. He was shown the exact room that he himself had used for days and nights of toiling in Torah. The holiness of his learning had permeated the atmosphere of the room and it affected the new owner, directing him towards a life of Torah.

We find this insight as well later in the Chumash when the twins Yaakov and Eisav were still in their mother's womb. When she went past a Beis Medrash, Yaakov struggled to leave, and when she walked past Avodah Zorah, Eisav struggled to exit. There's a famous question as follows. We know an angel teaches Torah to a child in the womb, why then did Yaakov struggle to go to the Beis Midrash when he already was learning from a holy angel? The answer is because his roommate was Eisav! Even with the best teachers, the influence of the environment is overpowering and Yaakov felt he must leave Eisav's proximity.