D'varim / Deuteronom 4:39 says loud and clear that there is no other G-d. Hashem is the only one.
"And you shall know this day and consider it in your heart, that the L-rd He is the G-d in heaven above, and upon the earth below; there is none else." D'varim / Deuteronomy 4:39.
The definite article הָֽ ('ha") in front of the word "elohim" (a title used to describe G-d, false gods, angels and even humans who are mighty / powerful judges) makes the translation "the G-d." הָֽאֱלֹ-הִ֔ים. Here is the Hebrew:
וְיָֽדַעְתָּ֣ הַיּ֗וֹם וַהֲשֵֽׁבֹתָ֘ אֶל־לְבָבֶ֒ךָ֒ כִּ֤י יְיָ֙ ה֣וּא הָֽאֱ-להִ֔ים בַּשָּׁמַ֣יִם מִמַּ֔עַל וְעַל־הָאָ֖רֶץ מִתָּ֑חַת אֵ֖ין עֽוֹד׃
Translations tend to translate this as "He is G-d", but the text acutally says "He is THE G-d." -- that is to say, "the One and Only G-D".
D'varim / Deuteronomy 4:35 (four verses earlier) is even more explicit....
אַתָּה֙ הָרְאֵ֣תָ לָדַ֔עַת כִּ֥י יְיָ֖ ה֣וּא הָֽאֱ-לֹהִ֑ים אֵ֥ין ע֖וֹד מִלְבַדּֽוֹ׃
"You have been shown these things so you should know that HaShem is the the One and Only G-D and there is no-one else apart from Him" (D'varim / Deuteronomy 4:35
Again we have The definite article הָֽ ('ha") in front of the word "elohim" ("the G-d"), but we also have אֵ֥ין ע֖וֹד מִלְבַדּֽוֹ׃ - no one else apart from Him.
G-d is ONE
Every single time G-d speaks in the Torah He speaks in the singular – one.
Never does G-d speak as a “plurality” (e.g. a trinity or more).
The fact that we are clearly told G-d is one (אֶחָד / eḥad – D'varim / Deuteronomy 6:4) is only one way we know He is not a trinity – throughout the Jewish bible this important “oneness” and “alone” (Yeshayahu / Isaiah 44:24) and “singularity” is repeated over and over so the lesson is not missed.
G-d is not a man (Bamidbar / Numbers 23:19),
“So said the L-rd. . . the ONE who formed you from the womb, “I (singular) am the L-rd . . .Who spread out the earth ALONE (לְבַדִּ֔י).” Yeshayahu / IIsaiah 44:24,
and we are told G-d is one (D'varim / Deuteronomy 6:4). But now see – it is I! I am the only One! There are no (other) gods with me! (Deuteronomy 32:39).
Over and over and over again we are told that G-d is ONE, alone, by Himself – SINGULAR.
#1 – “אֶחָד / eḥad ” means “one.” It is the same as the number one in English.
“G-d is one” (D'varim / Deuteronomy 6:4).
Some Trinitarians like to point out that “אֶחָד / eḥad ” can be a compound unity – (as in “one forest” which has many things in it).
אֶחָד / eḥad can be a compound unity (see B'reshit / Genesis 2:24 as an example) – but far more often it is an “absolute one” and not compound at all. The word "One" in this D'varim Deuteronomy 6:4 (the Shema) "the L-rd is One" is not a compound unity. It is definitely singular.
Examples of this “absolute one” can be found in Shmuel 2 / 2 Samuel 13:30: "Absolom has slain all the king's sons, and there is not one of them left" and 2 Samuel 17:12: "And of all the men that are with him we will not leave so much as one."
It is clear that just like the English word “one” the Hebrew word “אֶחָד / eḥad ” has a similar use – one means one! What about Deuteronomy 6:4 – the Sh’ma? “Listen, O Israel – the L-rd your G-d, the L-rd is ONE”? The word "One" in this Deuteronomy 6:4 is an adjective, and it describes the proper noun "the L-rd" (SINGULAR), which rules out the possibility of a "compound unity" in this passage.
#2 In Hebrew nouns are singular or plural – similar to English. Let’s look at B'reshit / Genesis 1:26 which begins with the subject of וַיֹּאמֶר vayomer “and he said”, which is a singular form. Hence B'reshit / Genesis 1:26 begins “and G-d (SINGULAR) said. If G-d were a trinity it would be plural. But G-d is ONE, not three.
וַיֹּאמְרוּ vayom'ru “and they said” can be found as in B'réshıt / Genesis 11:3, 11:4; 18:5, 18:9 as well as throughout the Torah – but whenever G-d speaks it is always singular “and He said.”
This is because G-d IS singular – one, not three.
#3 “That you will know that G-d, He (ה֣וּא – singular) is the (singular) Supreme Being and there is none besides Him (singular)" D'varim / Deuteronomy 4:35)
#4 "Now, O L-rd our G-d, deliver us from his hand, so that all kingdoms on earth may know that You ALONE, O L-rd, are G-d.” (Psalm 113:5)
#5 Before Me (SINGULAR) no god was formed, nor will there be one after Me (SINGULAR). I (SINGULAR), even I (SINGULAR), am the L-rd, and besides Me (SINGULAR) there is no Savior.” Yeshayahu / Isaiah 43:11
#6 So said the L-rd, your Redeemer, the ONE who formed you from the womb, “I am the L-rd Who makes everything, Who stretched forth the heavens alone, Who spread out the earth ALONE (לְבַדִּ֔י).” Yeshayahu / Isaiah 44:24.
#7 I am the L-rd, and there is no other; besides Me there is no G-d… I will strengthen you…I order that they know from the shining of the sun and from the west that there is no one besides Me; I am the L-rd and there is no other!” Yeshayahu / Isaiah 45:5-6
Bamidbar / Numbers 23:19, Shmuel 1 / 1 Samuel 15:29, and Iyov / Job 9:32 tell us that G-d is not a man. Some Christians may argue that Jesus “in the flesh” came later to explain away this fact – but the prophet Malachi destroys this argument when he says in Jesus. “For I, the L-rd, do not change.” Malachi 3:6. Becoming a man is certainly change!
There are missionaries who try to insist that the Hebrew word for one (אֶחָד / eḥad (masculine) ) is not really "one" at all. They try to insist that it is always a compound unity. Those missionaries will insist that יָחִיד yahid is only used to refer to a strict numerical oneness, whereas אֶחָד / eḥad has a wider range of usage that includes composite unities as well. This is total nonsense. אֶחָד ĕḥad is the numeral “1” in Hebrew. Actually it is the masculine noun; the feminine form is אַחַת aḥat). יָחִיד yahid translates more to "only."
The several declined inflections of the noun יָחִיד yahid occur in 12 scriptural verses:
יְחִידְךָ in B'réshιt / Genesis 22:2, 22:12 (only)
יְחִידֶֽךָ (the pausal form) in B'réshιt / Genesis 22:16 (your only)
יְחִידָה in Shoftim / Judges 11:34 (only child feminine)
יָחִיד in Yirm'yahu / Jeremiah 6:26, 'Amos Amos 8:10 and T'hillim / Psalms 25:16 (only son masculine)
הַיָּחִיד in Z'charyah / Zechariah 12:10 (his only)
יְחִידָתִי in T'hillim / Psalms 22:21 and 35:17 (my only one)
וְיָחִיד in Mishlei / Proverbs 4:3 (and only)
and the plural יְחִידִים in T'hillim / Psalms 68:7 (solitary, plural).
The term יָחִיד yahid applies to G-d only when we are stating that G-d is the only G-d. But G-d is not "alone" in the sense that He is surrounded at all times by His mal'achim (angels) chanting kadosh, kadosh, kadosh (holy, holy, holy) continuously.
There is a similar word often confused with יָחִיד yahid and that is yahad (יָחַד) which means "together."
Alone, in English or Hebrew, is a different word than the word "one."
It would be interesting to see how these missionaries would fit their re-definition of the word אֶחָד ĕḥad into verses like B'réshıt / Genesis 21:15 and B'réshıt / Genesis 22:2; did Hagar put her dying son, Ishmael, under multiple shrubs all at the same time “she threw the boy under ĕḥad [one] of the shrubs” -- or did G-d tell Abraham to take Isaac, his son, up onto many mountains "take him up... onto ĕḥad [one] of the mountains that I will tell you about”?
The word for "one" in Hebrew functions identically to the word in English -- thus while it can be a compound unity (as in one cluster of grapes) it can also be a definite one (one cell). Hebrew nouns are either masculine or feminine. In Hebrew the words for "one" are אֶחָד eḥad (masculine), אַחַת aḥat(feminine).
"You have been shown these things so you should know that HaShem is the the One and Only G-Dand there is no-one else apart from Him" (D'varim / Deuteronomy 4:35).