Why does the Torah write "Yom Echad" (one day) and not "Yom Rishon" (the first day), as it does on all the other days?
Rashi: This hints to the fact that it was only on the first day of the Creation that G-d was One; as the angels were not created until the second day. 1
Ramban #1 (citing Ibn Ezra): What the Pasuk means is that it was Erev and Boker of one day.
Ramban #2: The concept of 'first' only exists when there is a second 2 (such as in a sequence of days, objects or events), in which case the first one takes precedence over the second one, either in time or in some other way. Whereas here, the second day did not yet exist. 3
Gur Aryeh: The Pasuk does not mean, "the day on which Hashem was One," but rather, "the day of Oneness." A day is named for its events; on this day there was neither multiplicity nor divisiveness.
See R. Chavel's notes on the Ramban, where he queries the author. It is worth noting however, that the Ramban deliberately states, 'the second had not yet been made' - and that consequently, there was no sequence on which to base the second.
What is the significance of the statement, "And Hashem called the light 'day' ..."?
Ramban #1 (citing Ibn Ezra): Now that time was created, Hashem arranged the measure of day and the measure of night. And since Adam, who would eventually allot names to the various creations, had not yet been created, Hashem carried out that task here Himself. 1
Ramban #2: The naming refers to fixing the distinction between the two elements, "Your border (with reference to the sun) extends until here, and your border (with reference to the moon), until here" (Midrash Rabah). 2
Targum Yonasan (in the same vein as the Ramban): Hashem called the light day - for the world's inhabitants to work; and darkness, night - for them to rest.
Rashbam: Just as a king gives a new name to a subject whom he appoints to a high position (as we find by Pharaoh and Yosef), so too, did Hashem give a name to the light and darkness that He just created. 3 Consequently, from now on, whenever we find the term 'night and day' (for example, see Bereishis 8:22), it always refers to light and darkness that Hashem created on the first day. 4
Seforno: Even though the times of light and darkness did not apply in the same way as they do nowadays (seeing as the sun and moon had not yet been placed in the sky). 5
Pesachim 2a: It means that Hashem called light and appointed it in charge of the day; and darkness, and appointed it in charge of the night (and the one has no authority to encroach on the allotted time of the other - See Torah Temimah, citing the Yerushalmi Berachos, 8:6). 6
The same will apply to the naming of the sky (1:8), and to that of the dry land and the water (1:10). Whereas Adam named the living creatures exclusively.
The same will apply to the two other locations that we cited in note 1.
What we wrote in the previous note extends to this note as well.
Seforno, it appears, disagrees with the Rashbam's explanation. See Answer 5.
In the previous Pasuk, commenting on Hashem's division between light and darkness, the Seforno wrote, "During that time, when the initial light served, they were times of light and of darkness, which did not operate by means of the revolving planets, but by the Will of Hashem...."
See Torah Temimah, note 26.
Why did Hashem call the evening, "Erev," and the morning, "Boker"?
Ramban; Maharal (Chidushei Agados Vol. 1, p. 8, to Shabbos 25b): Hashem called the evening, "Erev," from the word 'le'Arev' (to mix) - because in the evening the shapes of all things mix together. He called the morning, "Boker," from the word 'le'Vaker' (to distinguish) - because that is when one can distinguish between them.
Bearing in mind that Adam would later assign names, "va'Yikra ha'Adam Sheimos le'Chol ha'Beheimah ... u'le'Chol Chayas ha'Sadeh" (2:20), why did Hashem Himself name the light and darkness (in this Pasuk); the sky (1:8); and the dry land and the seas (in 1:10)?
Oznayim la'Torah #1: Because Adam only named all living creatures. 1
Oznayim la'Torah #2: Because the three things that Hashem named were all connected with division - To divide between light and darkness, and between the upper and lower waters via the sky (which only Hashem could understand). 2
What are the implications of, "Vay'hi Erev Vay'hi Voker Yom Echad"?
Chagigah 12a: It implies that day and night were created already on the first day. 1
Chulin 83a: "Vay'hi Erev Vay'hi Voker" teaches us that night precedes day - in all Halachic matters other than Kodshim. 2
QUESTIONS ON RASHI
Rashi writes: "'One day' [Yom Echad] - In sequence, the Torah should have written 'the first day' (Yom Rishon)." Ramban asks - But perhaps the reason is that before the creation of the subsequent days, it was impossible to call it "first"?
Gur Aryeh #1: When Moshe transcribed the Torah in past tense, the subsequent days had already happened, therefore [from a literary perspective] it could have been called "first."
Gur Aryeh #2: Although the subsequent days had not yet been actualized, their potential had already been created. The six days of Creation comprise one whole unit, and therefore Day 1 could already have been called "first."
