Contributed by: R. Ezra Mizrahi
The midrash explains to us why the words "Ki Tob" were omitted on the second day of creation. On the second day, Hashem made a separation between the water which resides above the Rakiah (firmament) and below the Rakiah. There was no "new" creation of anything, but rather only a separation. Therefore, "Ki Tob" was not written for the second day. But then why on the fourth day "Ki Tob" was written? On the fourth day there was also "only" a separation- a separation between light and darkness.
Question: There was no "new" creation of anything as well- So why was "Ki Tob" written for the fourth day? The separation on the fourth day was between light and dark- a separation that is necessary for the two cannot dwell in the same place. Therefore, such a separation is deemed as "Tob" (Good) because of its inherent need, while the separation between water and water of the second day is not.
Why is the first day classified as "Yom Ehad" (Day One) and not "Yom HaRishon" (First Day)? "First" implies that it is the beginning of a series of days, when really the first day should not be considered the first day of creation. What was created on the first day, the hidden light for the Hachamim (Ohr HaGanooz), was removed from the world and saved for the future. To symbolize this hidden creation, the first day was counted as "Ehad" (one) and not "Rishon" (first), making it distinct from the rest of the days whose creations are apparent.