Hear, O Israel. When Moses proclaims that God is One, the statement is not confined to His sole essence, which is incomprehensible, but must be also understood of His power and glory, which had been manifested to the people; as though he had said, that they would be guilty of rebellion unless they abode in the One God, who had laid them under such obligations to Himself. Therefore he not only calls him Jehovah, but at the same time infers that He is the God of that people whom he addresses, "Thy God." Thus all other deities are brought to nought, and the people are commanded to fly and detest whatever withdraws their minds from the pure knowledge of Him; for although His name may be left to Him, still He is stripped of His majesty, as soon as He is mixed up with a multitude of others. Thus He says by Ezekiel, (Ezekiel 20:39,) "Go ye, serve ye every one his idols;" in which words He not only repudiates all mixed worship, but testifies that He would rather be accounted nothing than not be worshipped undividedly. The orthodox Fathers aptly used this passage against the Arians; because, since Christ is everywhere called God, He is undoubtedly the same Jehovah who declares Himself to be the One God; and this is asserted with the same force respecting the Holy Spirit.

These words form the beginning of what is termed the "Shema" ("Hear") in the Jewish Services, and belong to the daily morning and evening office. They may be called "the creed of the Jews."
This weighty text contains far more than a mere declaration of the unity of God as against polytheism; or of the sole authority of the revelation that He had made to Israel as against other pretended manifestations of His will and attributes. It asserts that the Lord God of Israel is absolutely God, and none other. He, and He alone, is Jehovah (Yahweh) the absolute, uncaused God; the One who had, by His election of them, made Himself known to Israel.

Hear, O Israel - שמע ישראל יהוה אלהינו יהוה אחד shema Yisrael, Yehovah Eloheinu, Yehovah achad. These words may be variously rendered into English; but almost all possible verbal varieties in the translation (and there can be none other) amount to the same sense: "Israel, hear! Jehovah, our God, is one Jehovah;" or, "Jehovah is our God, Jehovah is one;" or, "Jehovah is our God, Jehovah alone;" or, "Jehovah is our God, Jehovah who is one;" or, "Jehovah, who is our God, is the one Being." On this verse the Jews lay great stress; it is one of the four passages which they write on their phylacteries, and they write the last letter in the first and last words very large, for the purpose of exciting attention to the weighty truth it contains. It is perhaps in reference to this custom of the Jews that our blessed Lord alludes, Matthew 22:38; Mark 12:29, Mark 12:30, where he says, This is the first and great commandment; and this is nearly the comment that Maimonides gives on this place: "Hear, O Israel; because in these words the property, the love, and the doctrine of God are contained."
Many think that Moses teaches in these words the doctrine of the Trinity in Unity. It may be so; but if so, it is not more clearly done than in the first verse of Genesis, to which the reader is referred. When this passage occurs in the Sabbath readings in the synagogue, the whole congregation repeat the last word אחד achad for several minutes together with the loudest vociferations: this I suppose they do to vent a little of their spleen against the Christians, for they suppose the latter hold three Gods, because of their doctrine of the Trinity; but all their skill and cunning can never prove that there is not a plurality expressed in the word אלהינו Eloheinu, which is translated our God; and were the Christians, when reading this verse, to vociferate Eloheinu for several minutes as the Jews do achad, it would apply more forcibly in the way of conviction to the Jews of the plurality of persons in the Godhead, than the word achad, of one, against any pretended false tenet of Christianity, as every Christian receives the doctrine of the unity of God in the most conscientious manner. It is because of their rejection of this doctrine that the wrath of God continues to rest on them; for the doctrine of the atonement cannot be received, unless the doctrine of the Godhead of Christ is received too. Some Christians have joined the Jews against this doctrine, and some have even outdone them, and have put themselves to extraordinary pains to prove that אלהים Elohim is a noun of the singular number! This has not yet been proved. It would be as easy to prove that there is no plural in language.

Hear, O Israel,.... These are the words of Moses, stirring up the people to an attention to what he was about to say of this great and momentous article, the unity of God, to prevent their going into polytheism and idolatry. From one of the words here used, the Jews call this section Kiriathshema, which they oblige themselves to read twice a day, morning and evening (n); the last letter of the first word in this verse, "Shema", meaning "hear", and the last letter of the last word in it, "Echad", meaning "one", are greater than ordinary; which seems designed to excite the attention to what is contained in this passage:
the Lord our God is one Lord; the doctrine of which is, that the Lord, who was the covenant God and Father of his people Israel, is but one Jehovah; he is Jehovah, the Being of beings, a self-existent Being, eternal and immutable; and he is but one in nature and essence; this appears from the perfection of his nature, his eternity, omnipotence, omnipresence, infinity, goodness, self-sufficiency, and perfection; for there can be but one eternal, one omnipotent, one omnipresent, one infinite, one that is originally and of himself good; one self, and all sufficient, and perfect Being; and which also may be concluded from his being the first cause of all things, which can be but one; and from his relations to his creatures, as their King, ruler, governor, and lawgiver. And for this purpose these words are cited in Mark 12:29 but then they no ways contradict the doctrine of a trinity of persons in the unity of the divine essence, the Father, Word, and Holy Spirit, which three are one; the one God, the one Jehovah, as here expressed; see 1-John 5:7 and so the ancient Jews understood this passage. In an ancient book of theirs it is said (o) Jehovah, Elohenu, Jehovah (i.e. Jehovah, our God, Jehovah); these are the three degrees with respect to this sublime mystery; "in the beginning God (Elohim) created the heavens and the earth"; and again (p), Jehovah, Elohenu, Jehovah, they are one; the three forms (modes or things) which are one; and elsewhere (q) it is observed, there are two, and one is joined to them, and they are three; and when the three are one, he says to (or of) them, these are the two names which Israel heard, Jehovah, Jehovah, and Elohenu (our God) is joined unto them; and it is the seal of the ring of truth, and when they are joined they are one in one unity; which is illustrated by the three names the soul of man is called by, the soul, spirit, and breath; and elsewhere they say (r) the holy blessed God, and his Shechinah, are called one; see John 10:30.
(n) Mist. Beracot, c. 1. sect. 1, 2. (o) Zohar in Genesis. fol. 1, 3. (p) Ib. in Exod. fol. 18. 3, 4. (q) Ib. in Numb. fol. 67. 3. (r) Tikkune Zohar, Correct. 47. fol. 86. 2.

Here is a brief summary of religion, containing the first principles of faith and obedience. Jehovah our God is the only living and true God; he only is God, and he is but One God. Let us not desire to have any other. The three-fold mention of the Divine names, and the plural number of the word translated God, seem plainly to intimate a Trinity of persons, even in this express declaration of the unity of the Godhead. Happy those who have this one Lord for their God. It is better to have one fountain than a thousand cisterns; one all-sufficient God than a thousand insufficient friends. This is the first and great commandment of God's law, that we love him; and that we do all parts of our duty to him from a principle of love; My son, give me thine heart. We are to love God with all our heart, and soul, and might. That is, 1. With a sincere love; not in word and tongue only, but inwardly in truth. 2. With a strong love. He that is our All, must have our all, and none but he. 3. With a superlative love; we must love God above any creature whatever, and love nothing but what we love for him. 4. With an intelligent love. To love him with all the heart, and with all the understanding, we must see good cause to love him. 5. With an entire love; he is ONE, our hearts must be united in his love. Oh that this love of God may be shed abroad in our hearts!

With Deuteronomy 6:4 the burden of the law commences, which is not a new law added to the ten commandments, but simply the development and unfolding of the covenant laws and rights enclosed as a germ in the decalogue, simply an exposition of the law, as had already been announced in Deuteronomy 1:5. The exposition commences with an explanation and enforcing of the first commandment. There are two things contained in it: (1) that Jehovah is the one absolute God; (2) that He requires love with all the heart, all the soul, and all the strength. "Jehovah our God is one Jehovah."
(Note: On the majuscula ע and ד in שׁמע and אחד, R. Bochin has this remark: "It is possible to confess one God with the mouth, although the heart is far from Him. For this reason ע and ד are majuscula, from which the tsere subscribed the word עד, 'a witness,' is formed, that every one may know, when he professes the unity of God, that his heart ought to be engaged, and free from every other thought, because God is a witness and knows all things" (J. H. Mich. Bibl. Hebr.).)
This does not mean Jehovah is one God, Jehovah alone (Abenezra), for in that case לבדּו יהוה would be used instead of אחד יהוה; still less Jehovah our God, namely, Jehovah is one (J. H. Michaelis). אחד יהוה together form the predicate of the sentence. The idea is not, Jehovah our God is one (the only) God, but "one (or the only) Jehovah:" not in this sense, however, that "He has not adopted one mode of revelation or appearance here and another there, but one mode only, viz., the revelation which Israel had received" (Schultz); for Jehovah never denotes merely a mode in which the true God is revealed or appears, but God as the absolute, unconditioned, or God according to the absolute independence and constancy of His actions. Hence what is predicated here of Jehovah (Jehovah one) does not relate to the unity of God, but simply states that it is to Him alone that the name Jehovah rightfully belongs, that He is the one absolute God, to whom no other Elohim can be compared. This is also the meaning of the same expression in Zac 14:9, where the words added, "and His name one," can only signify that in the future Jehovah would be acknowledged as the one absolute God, as King over all the earth. This clause not merely precludes polytheism, but also syncretism, which reduces the one absolute God to a national deity, a Baal (Hosea 2:18), and in fact every form of theism and deism, which creates for itself a supreme God according to philosophical abstractions and ideas. For Jehovah, although the absolute One, is not an abstract notion like "absolute being" or "the absolute idea," but the absolutely living God, as He made Himself known in His deeds in Israel for the salvation of the whole world.