שְׁמַ֖ע יִשְׂרָאֵ֑ל יהוה אֱלֹהֵ֖ינוּ יהוה ׀ אֶחָֽד׃
Hear, O Israel! The LORD our God, the LORD is one.
THE LORD IS ONE - The word "Echad" (אחד) when translated to English retains the same meaning, "one." Though the word can refer to a compound unity, as this word does appear in other passages, itsimply points out that there is only one true G-d that exists. Some translations render the reading as "alone" to convey that point.
(ה) וַיִּקְרָ֨א אֱלֹהִ֤ים ׀ לָאוֹר֙ י֔וֹם וְלַחֹ֖שֶׁךְ קָ֣רָא לָ֑יְלָה וַֽיְהִי־עֶ֥רֶב וַֽיְהִי־בֹ֖קֶר י֥וֹם אֶחָֽד׃ {פ}
(5) God called the light Day and called the darkness Night. And there was evening and there was morning, a first day.
(ה) וּקְרָא יְיָ לִנְהוֹרָא יְמָמָא וְלַחֲשׁוֹכָא קְרָא לֵילְיָא וַהֲוָה רְמַשׁ וַהֲוָה צְפַר יוֹמָא חָד:
(5) Elohim called the light day, and the darkness He called night. It became evening and it became morning, one day.
A FIRST DAY - ָThis is the first instance of the word "Echad" appearing in the Tanakh. And we see a demonstration of the use of this word referring to a compound unity. Two separate times coming together to make one day (יום אחד).
(כד) עַל־כֵּן֙ יַֽעֲזׇב־אִ֔ישׁ אֶת־אָבִ֖יו וְאֶת־אִמּ֑וֹ וְדָבַ֣ק בְּאִשְׁתּ֔וֹ וְהָי֖וּ לְבָשָׂ֥ר אֶחָֽד׃
(24) Hence a man leaves his father and mother and clings to his wife, so that they become one flesh.
THEY BECOME ONE FLESH - Two separate individuals join to become one flesh. Adam and Eve are autonomous in their individuality but they need each other, so the two become "Echad." Further demonstrating the presence of a compound unity in the use of "Echad."
(ו) וַיֹּ֣אמֶר יהוה הֵ֣ן עַ֤ם אֶחָד֙ וְשָׂפָ֤ה אַחַת֙ לְכֻלָּ֔ם וְזֶ֖ה הַחִלָּ֣ם לַעֲשׂ֑וֹת וְעַתָּה֙ לֹֽא־יִבָּצֵ֣ר מֵהֶ֔ם כֹּ֛ל אֲשֶׁ֥ר יָזְמ֖וּ לַֽעֲשֽׂוֹת׃
ONE PEOPLE - A large grouping of individuals come together to form one group of people, (עם אחד). A further example of a compound unity, with respect to the word "Echad."
(טז) וְנָתַ֤נּוּ אֶת־בְּנֹתֵ֙ינוּ֙ לָכֶ֔ם וְאֶת־בְּנֹתֵיכֶ֖ם נִֽקַּֽח־לָ֑נוּ וְיָשַׁ֣בְנוּ אִתְּכֶ֔ם וְהָיִ֖ינוּ לְעַ֥ם אֶחָֽד׃
(16) Then we will give our daughters to you and take your daughters to ourselves; and we will dwell among you and become as one kindred.
BECOME ONE KINDRED (FAMILY) - Two sets of families with daughters of their own intermarry and become one large family. They're now "Echad" family.
(כב) אַךְ־בְּ֠זֹ֠את יֵאֹ֨תוּ לָ֤נוּ הָאֲנָשִׁים֙ לָשֶׁ֣בֶת אִתָּ֔נוּ לִהְי֖וֹת לְעַ֣ם אֶחָ֑ד בְּהִמּ֥וֹל לָ֙נוּ֙ כׇּל־זָכָ֔ר כַּאֲשֶׁ֖ר הֵ֥ם נִמֹּלִֽים׃
(22) But only on this condition will their representatives agree with us to dwell among us and be as one kindred: that all our males become circumcised as they are circumcised.
BE AS ONE KINDRED (FAMILY) - The same phrase is used in the context. Individuals coming to form one family unit, under the condition that they undergo circumcision.
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At first glance of Deuteronomy 6:4, one would think that it speaks to the oneness of G-d, but in actuality, it speaks of the truth of the plurality of G-d. The word used for “one” (echad) in Hebrew is most commonly used as a compound unity in contrast to “yachid.” “Echad” was used in Deuteronomy. So a lot of readers would be correct, (at first glance) regarding the correct reading of Deuteronomy 6:4. The original wording and writing (I believe) was left purposely ambiguous, in terms of the definition of “Echad” in this particular passage alone. It’s purely conjectural. However, judging by the context of the use of the word, it wouldn’t be (and couldn’t be) considered an overly outlandish and artificial interpretation of the word and the verse. Another thing I’d like to add, just as the word could mean “unity” (being many parts, yet one) as it relates to G-d himself, He (G-d) then stipulates how we should love him. And that one love is listed as many parts, being with all our mind, soul, and strength. G-d is “Echad” and our love for him should be “Echad.” Amen