לשתות העם, that the people could drink. The unusual construction is similar to Genesis 16,3 לשבת אברהם.

מה תריבון עמדי?; do you not know that I do not act arbitrarily but only carry out G’d’s orders?

'מה תנסון את ה?; if you really quarrel with me, this is equivalent to your quarrelling and testing the One whose agent I am. You are only endangering your own lives if you quarrel with G’d! If He becomes angry He will consider that He has to destroy you, seeing that He had demonstrated His power to you in deeds. We find Moses repeating this thought in Psalms 95,9 אשר נסוני אבותיכם בחנוני גן ראו פעלי, “when your fathers put Me to the test, tried Me, though they had seen My deeds.” [when someone who had never had a manifestation of G’d’s power “tests” Him, this is far less serious than when the Jewish people who had ample proof of G’d’s power would do the same. Ed]

עבור לפני העם, and their complaints will cease when they see that you are making an effort to provide their needs.

ומטך אשר הכית בו את היאור, your staff with which you had smitten the river so that the Egyptians had given up looking for water to drink, will now perform the opposite function and provide you with drinking water.

והלכת. from the camp to the rock.

והכית בצור ושתה העם, this will teach them that the staff is not an instrument which performs certain functions naturally, being unable to change its functions. It will show you that the staff is an instrument carrying out the will of its owner. This is why it can be used to perform opposing functions on different occasions.

ויבא עמלק, at the sound of the people’s being frustrated with thirst. This is what Moses meant when he recalled the incident 40 years later in Deuteronomy 25,18 describing the Israelites’ state of mind at the time as ואתה עיף ויגע, “you were tired and worn out.” We find the expression עיף linked to water also in Job 22,7 לא מים עייף תשקה, “You do not give the thirsty water to drink.” (Eliphaz accusing Job) We also find the word applied to earth itself in Isaiah 32,2 בארץ עיפה, “in a languishing land.”

ומטה האלוקים בידי, to show the people at what time he would be praying in order that they too would coordinate the time they offered their own prayers with that of Moses. The importance of this harmonising of prayers is demonstrated when the Talmud tells us that in the large synagogue of Alexandria they waved flags so that the people who could not hear the cantor could pray in harmony with him, nonetheless. (Sukkah 51).

את עמלק ואת עמו, fellow travelers from other nations who had joined Amalek in his attack against the Israelites.

כתוב זאת זכרון בספר, a reference to the portion in Deuteronomy 25,17-19.

ושים באזני יהושע, make sure that Joshua remembers all this. Moses carried out this command by building the altar and offering up the prayer declaring G’d as his flag.

מחה אמחה את זכר עמלק, not only the people but even their livestock. We know this from the instructions given by the prophet Samuel to King Sha-ul in Samuel 15,3 where the king is ordered to destroy utterly all the possessions of Amalek.

ויקרא שמו, he called the name of G’d in his prayer ה' ניסי. The matter is similar to the prophet Jeremiah saying in Lamentations 3,25: קראתי שמך ה'. Surely, there was nothing new in Jeremiah knowing the name of G’d. The point is that he addressed this attribute of G’d in that prayer. Moses addressed the attribute of G’d as the flag-bearer in Israel’s wars.

ה' נסי, “G’d is my exaltation.” The meaning is similar to Psalms 60,6 נתת ליראיך נס להתנוסס מפני קשט סלה, “You have given a banner to them that fear You, to raise themselves to its height before the might of wisdom.” In other words, the psalmist says that G’d will lend him the strength to cope with anyone trying to attack him and to overcome him. The same thought is expressed in Psalms 44,6 בשמך נבוס קמינו, “with the help of Your name we will vanquish those who rise up against us.”

ויאמר כי יד על כס י-ה, Moses explains the reason and purpose of his prayer being the fact that G’d Himself had sworn an oath to remain at war with Amalek from generation to generation. If G’d is at war with that nation, we as G’d’s representative on earth, must certainly also be at war with that nation. It is what our sages referred to when they said that three commandments cannot be fulfilled until the Jewish people are securely settled in the land of Israel, 1) appointment of a king; 2) destroying the last vestiges of Amalek; 3) the building of a permanent Temple. Moses therefore had prayed for the time when these three hallmarks of Jewish history could be attained. (Sanhedrin 20)