He is Our God, there is none else! Let us worship the Almighty with our acts of mercy and compassion toward humanity

כִּ֤י בֹעֲלַ֙יִךְ֙ עֹשַׂ֔יִךְ יי צְבָא֖וֹת שְׁמ֑וֹ וְגֹֽאֲלֵךְ֙ קְד֣וֹשׁ יִשְׂרָאֵ֔ל אֱלֹהֵ֥י כׇל־הָאָ֖רֶץ יִקָּרֵֽא׃ 

Because he who made you is your Master—
His name is “LORD of Hosts.”
The Holy One of Israel will redeem you—
He is called “God of all the Earth.”

 Isaiah 54:5

The God of Israel, its Master, the Holy One, is also the God of the whole Earth. The books of Isaiah proclaim One Sovereign God. No one else equal to him (I will follow the grammatical use of the male in reference to God as the Hebrew text does. This does not imply that God is like a human male, neither ignores that God at times is described with female adjectives). 

In Deuteronomy (6:4) and through the teachings of Moshe it is taught that there is Only One True God In the Christian tradition, Jesus of Nazareth followed these same Jewish teachings. He acknowledged and proclaimed the Reign of the Only One True God. In a prayer attributed to him (John 17:3) he says: αυτη δε εστιν η αιωνιος ζωη ινα γινωσκωσιν σε τον μονον αληθινον θεον (obviously he would not have added in a prayer speaking to God the phrase following this statement in many NT translations). Paul is attributed with the statement (1 Cor. 8:6) saying that "even if there were many other gods (or divine beings) for us (meaning the Jewish people who like him were followers of Jesus of Nazareth) there is One God, the Father" (A phrase stating that Jesus is a master or leader or lord follows it, added by a scribe just like the one at the end of John 17:3 in some editions). Perhaps a note from the scribe or could be original of Paul. But, he makes clear that only the Father is the true and only God. In the first letter to Timothy, he praises the Holy One of Israel by saying:

τω δε βασιλει των αιωνων αφθαρτω αορατω μονω θεω τιμη και δοξα εις τους αιωνας των αιωνων αμην

My interpretation:

"To the Eternal King, who never dies, no one has seen, the Only True God, be honor and glory forever and ever. Amen."

Other ancient religions, like Zoroastrism, recognizes and confess only one God, although absolut monotheism is taught only in Judaism and Islam. One of the most beautiful statements is found in the Qur'an, sura 112. The Baha'i Faith gathering everything good from every religion, it has helped humanity see the common connection, the Only One True God. There is only one God and one humanity. 

The prophet Zechariah (14:9) says that the day will come when all nations will recognize the Holy One of Israel as the Only One True God:

וְהָיָ֧ה יי לְמֶ֖לֶךְ עַל־כׇּל־הָאָ֑רֶץ בַּיּ֣וֹם הַה֗וּא יִהְיֶ֧ה יי אֶחָ֖ד וּשְׁמ֥וֹ אֶחָֽד׃

We conclude with this verse after the chanting of Aleynu. This closing prayer in our liturgy was converted in a song by the Jewish composer Julius Chajes, z"l, and heard not only in our Reform Jewish temples, but among some Christians. Here is a version recorded by a Christian choir:

 

 Let us worship the Almighty with our acts of mercy and compassion toward humanity.