In the six days of creation in Bereshit, Hashem created everything that it supposed to be created. Hashem completed all the creations (מאין יש). All the creations afterwards were done according to the rules of nature. However, according to the Ramban, Lice (third plague) was a new creation (בריאה חדשה) since a Hashem created the lice from the dust of the earth. My understanding is that this creation is not according to the rules of nature. How do you explain this issue? Many thanks,

The Ramban on Shemot 8:15 offers his explanation of why Pharaoh's sorcerers were unable to reproduce the lice. He says that unlike the plagues of frogs in which the frogs were gathered and were not created, in the plague of lice Hashem created new lice. In fact all the plagues were miracles and did not follow the rules of nature. This issue is explained by Chazal and many of the Rishonim more or less along the same lines. Within the laws of nature G-d "built in" the changes which were to happen over the generations. Thus for example when G-d created the sea, He already had set down conditions that the sea split for the Jewish people when they left Egypt. When G-d created the sun on the fourth day of creation it was already placed in the sun's nature that it pause in the time of Yehoshua. ( See בראשית רבה ה:ד, ספר כוזרי ג: עג, רמב"ם פירוש המשנה לאבות ה:ה, רבינו בחיי שמות יד:כז) The same would therefore apply to what the Ramban says about the lice. The Ramban himself points out in his commentary on the Torah the different instances where the specific changes in nature which are mentioned in Pirkei Avot 5:5 were applied. (See Ramban Shemot 16:6, Bamidbar 22:23).