The Medrash Rabbah (39:1) relates that Avrohom Avinu recognized that this world must have a ruler. Hashem then peaked out at him and said, “I am the Master of the tower.”
The Izhbitzer Rebbe zy”a (Sefer Mei Hashiloach) explains that Avrohom contemplated all the changes that occurred in the world during the generation of the mabul and the dor haflagah. This led him to wonder who caused all this to occur. Hashem replied that this is not the correct approach. It is the way of the nations of the world to take heed when something wondrous occurs in the world and to wonder who caused it to happen. However, when everything seems to be operating according to the laws of nature, they don’t bother to wonder who is running the world. They don’t understand that even nature cannot operate on its own without Hashem guiding it.
Klal Yisroel, on the other hand, understands that Hashem created every aspect of this world. They believe that the world could not exist even for a moment without His guidance.
Accordingly, the Medrash is saying that when Avrohom was amazed by the miraculous occurrences and wondered who caused them, Hashem told him “lech lecha”, go away from this mindset and recognize that He is the ruler of the tower, even when things seem to be running naturally.
