Commentary
The first of the above verses (51) was revealed in response to a hostile Jewish demand. As mentioned by Baghawl, Qurtubi and others, the Jews asked the Holy Prophet ﷺ ، "How can we believe in you while you neither see Allah Ta’ ala, nor do you speak to Him face to face, as Sayyidna Musa (علیہ السلام) used to see and converse with Allah Ta’ ala?"
The Holy Prophet ﷺ told the Jews that it is wrong to say that Sayyidna Musa (علیہ السلام) has seen Allah Ta’ ala. Then this verse was revealed to announce that it is not possible for any human being to converse with Allah Ta'ala face to face in this world. Sayyidna Musa (علیہ السلام) also did not hear Allah Ta'ala face to face, but only heard the voice from behind a curtain.
This verse also tells us that there are only three ways in which Allah Ta'ala speaks to a human being. One is ` wahy' which is infusion of something in the heart. It can happen while one is awake, and it can also happen during sleep in the form of a dream as stated in many ahadith that the Holy Prophet ﷺ said, اُلقِیَ فی روعی (This has been infused in my heart. And the dreams of the prophets (علیہم السلام) are also a form of wahy, because Shaitan cannot find his way in them. In case of dreams, the words do not usually come from Allah Ta’ ala; only the subject matter is infused in the mind which is then rendered by the prophets in their own words.
The second way in which Allah may address a person, as mentioned in the above verses, is that Allah speaks from behind a curtain, as happened to Sayyidna Musa (علیہ السلام) on Mount Tur, where he heard the speech of Allah Ta’ ala, but did not see Him. Therefore he asked Allah Ta'ala to show Himself. The reply was in negative, as mentioned by the Holy Qur'an in surah A'raf (7:143).
And this curtain which prevents man from seeing Allah Ta'ala is not something which can hide Allah Ta’ ala, because nothing can hide His All-Pervasive Light. Rather, it is the weakness of man's vision that becomes a curtain against seeing Allah. That is why when his vision would be strengthened in Paradise, every dweller of Heaven will be favoured with ability to see Allah Ta’ ala, as per the creed of Ahl-us-Sunnah wal-Jama` ah in accordance with the explanations of correct ahadith.
This rule that no one can converse face to face with Allah Ta’ ala, without any curtain in-between, pertains to this world. The specific mention of ` human being' in this verse is because the intention here is to address mankind. Otherwise, apparently Allah Ta'ala does not speak face to face even with the angels, as stated by Sayyidna Jibra'i1 (علیہ السلام) in a narration of Tirmidhi, "I had become very close, and yet there were seventy-thousand more curtains." And if the face to face conversation of the Holy Prophet ﷺ with Allah Ta'ala during the Night of Ascension (Lailat-ul-mi` raj) is proved, as stated by certain learned persons, it would not negate this rule, because that conversation did not take place in this world, but in the Heavens. (Allah knows best).
The third method is mentioned in the verse as أَوْ يُرْسِلَ رَسُولًا "that He sends a messenger" (42:51). The messenger could be Jibra'il (علیہ السلام) or any other angel who may carry Allah Ta’ ala's message, and read it out to the prophet. And this has been the most common way. The whole of Glorious Qur'an has been revealed in this fashion through angels. It should be noted that the word ` wahy' has been explained above to mean infusion in mind or heart only, but this word is often used for all kinds of Divine discourses also, as narrated in a lengthy hadith of Bukhari where the message sent through an angel has also been termed as one kind of ` wahy'. And there are two forms in which the angel carries the message. Sometimes he appears in his original form, and sometimes in the human form. (Allah knows best).