There are always those who deny the existence of miracles. They claim that the works of Hashem are simply natural occurrences. This was the attitude of many nonbelievers in regard to the splitting of Yam Suf. They claimed that an earthquake or an accident of nature caused the sea to split.
To prevent any such beliefs, Hashem increased the miracle. Rashi says that not only was the Yam Suf split, but also all of the waters in the world were split. Because of this, no one could deny that this truly was an act of God.
As the Jews were standing by shore of the Yam Suf watching their enemy come closer, they did not know what to do. Suddenly, Nachshon ben Aminadav jumped into the Yam Suf with full confidence that Hashem would save him. As he touched the water, it parted and allowed the Jews to pass through. It was Nachshon’s faith in Hashem that led to Bnai Yisrael’s being saved.
Another miracle that Hashem gave the Jewish People was the מן. Every morning the מן dropped from the sky. Every Jew was ordered to collect a set amount of מן. They were not to take more than they needed, as those who did displayed a lack of faith in Hashem because He said that He would provide the מן daily. Even without this special assurance, these people would still have been wrong: Hashem is always performing miracles for His people. The fact that the Jews are still in existence after thousands of years of persecution is a miracle. In Israel today, miracles occur daily.
Sometimes, though, we take these daily miracles for granted. They happen all the time, so we do not bother to think about them. It is important to take the time to appreciate all of the miracles that Hashem performs, but in order for Hashem to perform great miracles for us, we have to show the same faith that Nachshon ben Aminadav showed at Yam Suf.