Le Deutéronome 6:4 Commentaire : Rashi, Chizkuni, Da'at Zekenim & Ramban

ה׳ אלהינו ה' אחד means, The Lord who is now our God and not the God of the other peoples of the world, He will at some future time be the One (sole) ה׳, as it is said, (Zephaniah 3:9) “For then I will turn to the peoples a pure language that they may all call upon the name of the Lord", and it is further said, (Zechariah 14:9) “In that day shall the Lord be One (אחד) and His name One" (cf. Sifrei Devarim 31:10).

שמע ישראל, “Hear O Israel!” we have an aggadic text according to which the letter ע in the word שמע is supposed to be “hanging”, i.e. not written directly on the line with the other letters in that word. The reason for this is supposed to be that G-d created the universe by using this letter. What is meant by this? Israel is one amongst 70 nations, the number of nations are one seventieth of the number of beasts that populate the earth. The number of fourlegged red blooded beasts on earth are one seventieth of the number of species of birds. The species of birds amount to one seventieth of the species of fish, which in turn are one seventieth of the number of different malignant forces, evil spirits, which in turn are one seventieth of the number of angels in heaven. The Lord G-d, presides over all of these creatures as the sole ruler. This is what the liturgist referred to when in his poem entitled ראשית. (No source provided)

שמע ישראל ה' אלוקינו ה' אחד, “Hear, O Israel, the Lord is our G–d, the Lord alone.” This verse would not be complete unless G–d’s name had appeared in it three times. If the Torah had only written: שמע ישראל ה' אחד, “Hear Israel, the Lord is one,” every other nation in the world would have claimed that their national deity was also unique for them. By adding the word: אלוקינו, “our G–d,” every reader would know that the subject is the G–d of Israel. If we would only say: “the Lord our G–d is one,” the impression would be left that He is one of a number of deities. The correct translation of the way Moses described G–d in our verse is: “the Lord Who is our Master is unique as a Master, and there is none beside Him.” When reciting this line in our prayers it is necessary to introduce this prayer with the words: א-ל מלך נאמן, “G–d who is a true king.” The reason that the authors of the prayer book have seen fit to add these three words is that by adding them the three paragraphs of this prayer including the line ברוך שם כבוד מלכותו, “blessed be the glory of His Kingdom,” total 248 words, a number which equals the 248 limbs in our bodies. This is hinted at by Solomon in Proverbs 4,4: שמר מצותי וחיה “Keep My commandments and you will live.” G–d is portrayed as saying that if you (Israel) keep My commandments, I will keep you alive.” Rabbi Shimon ben Chalafta explained this concept by means of a parable: a king possessed a vineyard in the central part of the land of Israel, whereas his residence was in the northern part of the country. Another king possessed a vineyard in the northern part of Israel, whereas his residence was in the central part of the country. Each king had to travel at least once a year from his residence to his vineyard to make sure the vineyard was being tended properly. Eventually, these two kings met one another and each complained to the other about the inconvenience of having to visit his vineyard every year. They made an agreement that each king would take care of the other’s vineyard, an arrangement that saved each of them a lot of time and inconvenience.