Let us mention a point first: In the Qur'an, Allah does not always address Himself as “We” instead of “I”. The verses are not always arranged this way. According to the context, the forms of address change; sometimes “I”, sometimes “We”, etc.
If the following verses are understood, this point will be clear:
“O Children of Israel! Remember My favor that I bestowed upon you, and fulfill My covenant (which I made with you through your Prophets), so that I fulfill your covenant, and of Me alone be in awe and fear (in awareness of My Power and of your being My servants).” (The Qur'an, Al-Baqarah Surah, 2:40)
“And when (O Messenger) My servants ask you about Me, then surely I am near: I answer the prayer of the suppliant when he prays to Me. So let them respond to My call (without hesitation), and believe and trust in Me (in the way required of them), so that they may be guided to spiritual and intellectual excellence and right conduct.” (The Qur'an, Al-Baqarah Surah, 2:186)
“Pray to Me, (and) I will answer you.” (The Qur'an, Al-Mumin Surah, 40:60)
“I have not created the jinn and humankind but to (know and) worship Me (exclusively).” (The Qur'an, Adh-Dhariyat Surah, 51:56)
In many other verses like these above, the translations of which we provided here as examples, our Lord mentions Himself with the pronouns of the first person, “I”. If these verses are carefully analyzed, it is seen that the expressions “ My covenant”, “so that I fulfill your covenant”, “ And when My servants ask you about Me”, “ Pray to Me” are related directly to Allah Himself and He doesn't accept any means or any intermediaries in between. Most of the verses in which Allah addresses Himself as “I” are always about Himself.
In the verses where the form of address is “We”, generally there is a means in between. For example, in the verses about the revelation of the Qur'an, it is said: “We sent it down.” As all verses are sent down by way of revelation, here the means between Allah and the Prophet, peace and blessings upon him, is the angel Gabriel, peace be upon him. In the verses such as “We caused the cloud to shade you.” (The Qur'an, Al-Baqarah Surah, 2:57), too, the One Who had the work done is Allah, and the ones who did the work are the angels who are in the position of “Allah's officers.” However, we should not compare this similitude of “officer” made here with the officers that humans have to hire in order to make their work easier. There are officers in the society because we are incapable to handle everything, while Allah puts angels to work in order to announce His power which dominates the universe and to convey His greatness through them, not because-God forbid- He needs them.
After all, many scholars learned in the explanation of the Qur'an say that in such verses Allah addresses with His own greatness and power, with His Godhead and majesty. That's to say, Allah addresses with His beautiful Names and attributes and thus informs about His greatness and majesty.
For instance, in the verse “Indeed it is We, We Who send down the Reminder in parts, and it is indeed We Who are its Guardian.” (The Qur'an, Al-Hijr Surah, 15:9), there are four words with the meaning “We”. Here, both the greatness and majesty of Allah is emphasized and the importance of the point is consolidated with pronouns.
Scholar of the Qur'an's explanation, Abu's-Suud Afandi, says in the explanation of the verse above: “We sent down the Qur'an with the greatness of Our glory and with Our Loftiness.”
In the explanation of the expression “Inna”, which means “We”, in Al-Kauthar Surah, Fahruddin Razi says: “Here what is meant with 'We' is to demonstrate the greatness of Allah.” He continues: “This is because it is Allah the Owner of the Heavens and the Earth who gives Kauthar (abundant good) to the Prophet (PBUH) as a gift. And the gift gains worth and greatness according to the greatness of its giver.”
Bediuzzaman Said Nursi, one of the leading contemporary Islamic scholars, deals with the expressions “Inni” (I) and “Qulna” (We said) in the 34th verse of Al-Baqarah Surah and says:
“It is a sign of the fact that in the deed of creating and bringing into existence there is no means/intermediary, and that in His speech and address there is means/intermediary.”
He continues to explain the pronoun “Na” (We) in the 105th verse of An-Nisa Surah:
“Just as in this verse the plural pronoun “Na” (We), which denotes greatness, is a sign that there is intermediary in revelation; so too the Name of Majesty, Allah, which is in the singular form, in the expression “how Allah has shown you” is a sign that there is no intermediary in inspiring meanings.” (Risale-i Nur Collection, İşaratü'l-îcaz, p. 230)
Then, it should not be understood from the verses in which Allah addresses Himself as “We” that-God forbid- Allah is more than one.
Don't we, too, sometimes say “We did.” when we actually refer to the things that we did on our own?