בעשרה מאמרות נברא העולם (אבות ה:א)

The Rambam (Maimonides) explains that HaShem could have created the world with just one utterance.  He could have said, for example, “ויאמר אלוקים יהיו השמים והארץ ויקוו המים” (and HaShem said there should be heaven and earth and the waters should ingather) or something in this vein.  The reason why HaShem dedicated a special sentence for each of the ten separate parts of creation was to teach us how important each and every part is. We should be careful not to destroy a part of His creation – even if the other nine parts remain. As we know, each person is a small world on its own, and we should look after our own small world to not sin with it or cause it to lose its source of life.  The wicked people who disregard their own life or that of others will be punished tenfold, while the righteous will be rewarded ten measures for looking after their body – their own small world – and that of others!  (Mussar Avos)