Exode 17:15

And Mosheh builded an altar, and called the name of it, The Word of the Lord is my banner; for the sign which He hath wrought (in this) place was on my behalf.

הי נס, the staff of G’d [in Moses’ hand Ed.] had become a miracle or equivalent to a flag, (an inspiration) on the hill on which Moses was positioned. Moses prayed that G’d would also use it in this manner in the future in order to conduct the war against Amalek, because G’d had already now given the commandment and assurance that He would completely wipe out even the memory of Amalek [this being the inspiration of the anti God forces on earth. Ed.] This is also what is spelled out in verse 16. 'ויאמר כי יד על כס י-ה וגו, this is why I call the altar ה' נסי, “G’d is my banner, my flag.” This is the same as when a father calls his son Eliezer, which means the same thing in Hebrew. (compare Exodus 18,4 where the reason for Moses calling his son by that name is explained.) Also the name Emanuel means the same, i.e. two words עמנו א-ל, “G’d is with us.” (Isaiah 7,14) G’d raised His hand in an oath, swearing by His throne that He would conduct ongoingמלחמה לה' בעמלק מדר דר, war against Amalek throughout the generations until he would be wiped out completely. Invoking the word יד here in connection with G’d’s utterance (as opposed to visible action) is the same as the line כי אשא אל שמים ידי, “I raise My hand to heaven” in Deuteronomy 32,40 it clearly is the formula for G’d swearing an oath. This is the plain meaning of these words. There are some who explain that when a king will sit on the throne of Israel, such as King Sha-ul, the time will have come to wipe out Amalek completely. I cannot accept this interpretation at all, as if it were correct, the Torah should have written כי תהיה יד אל כס י-ה “when the throne of Israel will be occupied by a real powerful king, representing G’d on earth.” The meaning of the words כי יד על כס י-ה is: “whenever a deliberate threat is posed against the kingdom of G’d on earth, etc.”

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.”