Chazal write that Moshe sinned with the word "Az," saying "u'me'Az Basi..."; and he rectified the sin with "Az" when he said "Az Yashir" (15:1). What is the significance of this word?
Maharal (Gevuros Hashem, Ch. 47, p. 184): "Az" refers to 'the specific present' ('Atah ha'Meyuchad')," an indivisible unit of time. Thus, this term indicates Oneness. 1 When Hashem shows his mastery over opposite forces, (such as turning the dry land into sea, 2 or the sea into dry land, 3 ) it shows his Oneness. The Torah then uses the word "Az," spelled Alef-Zayin, value of one above seven, indicating that Hashem is One, over and in control of the numerous forces of nature. 4 Moshe was connected to this great level, until even he erred about it in our Pasuk, by attributing the worsening state of Yisrael to the Midah of "Az." Moshe later repaired this error, when he praised Hashem for His miracles and wonders with "Az." 5
Time is a property of the physical, as both time and physical (space) have dimensions, and are divisible. See Maharal (ibid. Ch. 46). A moment (Eis) has no duration, and is indivisible; this alludes to the Oneness of Hashem - oneness that cannot be divided, because division is a physical concept. (EK)
In the generation of Enosh; "Az Huchal etc." (Bereishis 4:26; and see Rashi to Bereishis 6:4).
At Keriyas Yam-Suf; "Az Yashir" (15:1).
In this world, Hashem's guidance is 'distributed' along seven Midos; but they all emanate from One Source, Hashem Echad. This is the meaning behind the word "Az." (EK)
Maharal (loc. cit. p. 185): How was Moshe connected to this Midah of "Az"? Moshe was the 'Ish ha'Elokim,' who prophesied "through a clear lens" (Rashi to Bamidbar 12:6) - unclouded by physicality.
