וַיִּקְרָ֨א אֱלֹהִ֤ים ׀ לָאוֹר֙ י֔וֹם וְלַחֹ֖שֶׁךְ קָ֣רָא לָ֑יְלָה וַֽיְהִי־עֶ֥רֶב וַֽיְהִי־בֹ֖קֶר י֥וֹם אֶחָֽד׃ (פ)
上帝稱光為「晝」，稱黑暗為「夜」。有晚上，有早晨，這是一日。
Rashi
יום אחד THE FIRST DAY (literally, one day) — According to the regular mode of expression used in this chapter it should be written here “first day”, just as it is written with regard to the other days “the second”, “the third”, “the fourth”. Why, then, does it write אחד “one”? Because the Holy One, blessed be He, was then the Only One (Sole Being) in His Universe, since the angels were not created until the second day. Thus it is explained in Genesis Rabbah (Genesis Rabbah 3:8).
Ibn Ezra
“And He called” – The hey of layla is added, and it [i.e., the word] is accented on the penultimate syllable, and it is always masculine. “Evening” [erev - close in meaning to darkness, and it’s called thus since forms are mixed together [nitarvu i.e., indistinct]. “Morning” [boker] – the opposite of evening, for a person is able to check [l’vaker, i.e., to distinguish] between forms. The meaning of “one day” is referring to the rotation of the sphere. There is a secret to the midrash of six thousand. And after it has said that the light is called day, it isn’t possible that the evening should be called day, rather its explanation is “it was evening and also morning of Day One”, for if it was [referring to] the evening and morning(g of one day, what would be the meaning of “a second day”?
Ramban
AND G-D CALLED THE LIGHT DAY. The verse states that time was created, and G-d made the length of the day and the length of the night.
The purport of the word vayikra (And He called) is [to indicate that] since Adam later gave names [to all the beasts, the fowl, etc.],90Further,2:20. it states that those things which were made before his existence were given names by G-d. This is the opinion of Rabbi Abraham ibn Ezra.91In Verse 8.
The correct interpretation is that the matter of calling a name here indicates the division which bounded them when they assumed their form. Thus did the Rabbis say:92Bereshith Rabbah 3:7. “[G-d said to the light,] ‘The day shall be your boundary,’ [and to darkness He said,] ‘The night shall be your boundary.’”
The purport of the word vayikra (And He called) is [to indicate that] since Adam later gave names [to all the beasts, the fowl, etc.],90Further,2:20. it states that those things which were made before his existence were given names by G-d. This is the opinion of Rabbi Abraham ibn Ezra.91In Verse 8.
The correct interpretation is that the matter of calling a name here indicates the division which bounded them when they assumed their form. Thus did the Rabbis say:92Bereshith Rabbah 3:7. “[G-d said to the light,] ‘The day shall be your boundary,’ [and to darkness He said,] ‘The night shall be your boundary.’”