The expression "WE" in the Noble Quran refers to the Supreme Power to Allah. It is an expression of the Royal Decree, NOT plurality. For that reason the term "We" is always followed by the singular part of speech in all such verses. For example, "We were Witness to their judgment" (21:78). "We are the All-Knower." (21:81) and many more similar verses.
When Allah Almighty addresses Himself as "We" in the Noble Quran, it must be known that this expression symbolizes the standing of royal decree and the eloquent language that is befitting while referring to the Supreme Majesty of the Almighty, the One and Only. It is NOT a reference to plurality.
The expression "We" is a feature of the literary style in Arabic as in various other languages including English. The style of using the term "we" is often observed in speeches and announcements of monarchs issuing decrees such as "we have ordered" or "we have decided" or "we have suspended" etc. In English this protocol is known as the the "royal we." The speaker is one and the plural "we" is symbolic of high status and respect.
Whenever Allah uses the expression "We," it refers strictly to Himself only, the All-Powerful and the All-Knower. It is a symbol of the highest status and greatest of respect which only Allah is entitled to and NONE else. The term "We" in the Quran is a gesture of Allah's unlimited glorification. IT DOES NOT INDICATE PLURALITY.
Those who may argue claiming that the term "We" defines plurality are wholly unaware of two very important and basic factors:
(1) Their ignorance of the principal ideology that establishes the essence of the Noble Quran, that is, the ideology of strict MONOTHEISM.
(2) Ignorance of certain rules of Arabic and English grammar.
There are any number of verses in the Quran, from start to finish, that assert loud and clear that Allah is ONE, and NONE has the right to be worshiped except Him. No reader of the Quran with the slightest of common sense and vision can overlook this most vital commandment and principle of the Quran. Surah 112, At-Tawheed (meaning 'Unity'), which is known as the 'essence of the Quran,' emphasizes entirely on the Oneness of Allah.
"Say He is Allah the One and Only!
Allah the eternally Besought of all!
He begetteth not nor was begotten.
And there is none comparable unto HIM."
(At-Tawheed, 112:1-4) [Also known as Surah Al-Ikhlas].
Thus, the subject on the unity of Allah, The Almighty, is crystal clear throughout His Final Message. There is absolutely NO room for any doubts, confusion nor ambiguity.