Exode 15:1

Behold: then sang, Mosheh and the sons of Israel this song of praise before the Lord and saying they said: Thanksgiving and praise we bring before the Lord Most High, who is glorified above the glorious, and exalted above the exalted; who punisheth by His Word whomsoever glorifieth himself before Him. Therefore when Pharoh the wicked bare himself proudly before the Lord, and, being uplifted in his heart, followed after the people of the sons of Israel, their horses and their chariots He threw and buried in the sea of Suph.

AZ YASHIR MOSHEH'(THEN MOSES WILL SING). Rashi comments: “[Then], when Moses saw the miracle, the thought came to his heart that he would sing a song, (he will sing) — is used here by the Torah, since the expression denotes Moses’ thought that he should sing. Rashi thus interprets yashir to be a pure future. Ramban will differ with this interpretation. and thus he actually did, [as it is said], and they spoke, saying. Similarly, az yedabeir Yehoshua means that when he saw the miracle [mentioned there], his heart prompted him to speak, and thus he actually did, [as it is said], and he said in the sight of Israel. The same interpretation applies to the Song of the Well, which begins with the words, az yashir Yisrael, and Scripture explains after that, Spring up, O well, sing ye unto it. This part of the verse shows that the preceding expression, az yashir Yisrael, denotes intent of heart to sing, thus: “Then, when they saw the miracle, their hearts told them that they should sing,” and so they did, as is indicated by the expression sing ye unto it, which is the call to the people to sing. Likewise: az yivneh Shlomoh, which the Sages of Israel explained it as meaning that he proposed to build but did not build it. as a prefix of the imperfect verb, [i.e., the future tense of a verb], indicates an intent to do a thing” (Rashi). This explanation serves to clarify the literal meaning of the text.”
But what will the Rabbi [Rashi] say concerning these verses: ‘Ya’asu’ [literally: “They will make”] a calf in Horeb; How oft ‘yamruhu’ [literally: “will they rebel”] against Him in the wilderness, and ‘ya’atzivuhu’ [literally: “they will grieve Him”] in the desert!, 78:40. The entire psalm is so written [in the future tense]: yaharog [literally: “He will destroy”] their vines with hail;, Verse 47. y’shalach [literally: “He will send”] among them swarms of flies, Verse 45. — [when all of these verbs refer to past events]! Similarly: And from whence ‘yavo’u’ [literally: “shall they come”] unto thee? Of the wounds which the Arameans ‘yakuhu’ [literally: “shall smite him”]., 8:29. Likewise, Now Moses ‘yikach’ [literally: “will take”] the tent does not denote a continuous event,, where the future tense “shall take” is used, the action is not one of continuous happening and still the future tense is used! since he took it only once. Instead, [we must conclude that] it is the way of Scripture to use the future tense in place of the past form, and in many places the reverse is quite usual. The reason for this is that it is a distinctive way of language for a narrator of an event to place himself at a certain point of time which he desires, and he then alludes to the event. At times, he places himself at the moment of the action, and he speaks of it in the present tense as if he is watching it from its very beginning. He would say, “Israel is singing,” as if they were singing right before him, and so also in other cases. However, at times the narrator places himself after the event and says, “This has already been done.” It is all a matter of conveying an event realistically. It is for this reason that this interchangeable use of the tenses occurs in matters of prophecy.

גאה גאה, victory in war is called גאות on several occasions. For instance, Moses says in Psalms 94,2 השב גמול על גאים, “give the victors their just deserts.” We find the expression בית גרים יסח ה' in Proverbs 15,25 where it means: “G’d will tear down the house of the victors.” [The author quotes a few more such examples, but I have not been able to find proof in this that the verses speak of “victors in war,” rather than arrogant people in whatever vocation. Ed.]

רמה בים, another way of saying השליך, “He flung (into the sea).” Psalms 78,9 speaking of רומי קשת, also uses the root רמה as “throwing, flinging.”

אז ישיר, he agreed to sing this song.

כי גאה גאה, He alone is entitled to feel this sense of superiority seeing He is the source of all goodness in the universe. This is in contrast to Pharaoh who boasts about having created the Nile as the source of Egypt’s affluence, (Ezekiel 29.3) a totally spurious claim.

סוס ורוכבו רמה בים, a reference to Pharaoh and his horse. Compare Psalms 136,15 ונער פרעה וחילו בים, “He tossed Pharaoh and his armed might into the Sea.”

אז ישיר משה, “this is when Moses broke out with a song, etc.;” Moses now apologised for when in frustration he had said to G–d, also using the word מאז, “from then,” that since he had assumed his position the fortunes of the Jewish people had worsened (Exodus 5,23). He therefore used the same word when now singing G–d’s praises. An alternate interpretation: the numerical value of the word אז is 8. He hinted that the Jewish people had merited this miraculous salvation on account of the circumcision which is performed on the eighth day of the infant’s life. The verse לגוזר ים סוף לגזרים, “Who splits apart the Sea of reeds into separate sections,” (Psalms 136,13) is used as a Scriptural reference to this. The Hebrew word וימל, “he circumcised,” describing Avraham performing circumcision in Genesis 17,23, is translated by the Targum as וגזר.