Praise be to Allah, and peace and blessings be upon the Messenger of Allah.
It is not permissible for a Muslim to imagine Allah تعالى in the form of a human being, light, or any other form belonging to created beings. A Muslim is not required in the first place to imagine or visualize the Essence of Allah, because Allah سبحانه وتعالى has no equal or likeness, and a created being cannot comprehend the reality of His Essence and Attributes. What is obligatory is to believe in what Allah has described Himself with, and what His Messenger صلى الله عليه وسلم described Him with, in a manner befitting His Majesty and Greatness.
Allah تعالى says:
﴿لَيْسَ كَمِثْلِهِ شَيْءٌ وَهُوَ السَّمِيعُ الْبَصِيرُ﴾
[Ash-Shura: 11]
Allah سبحانه is without equal, likeness, counterpart, or peer, and He is far above resembling His creation.
Therefore, any image or form that a person imagines in his mind cannot be the reality of Allah تعالى. What a person is capable of imagining is limited to what he has known from created things, whereas Allah سبحانه وتعالى is far greater and more exalted than any created being's imagination can encompass.
Allah تعالى says:
﴿وَلَا يُحِيطُونَ بِهِ عِلْمًا﴾
[Taha: 110]
It is neither an act of worship nor part of sound creed for a Muslim to try to form a mental image of Allah تعالى or imagine His form.
Rather, the obligation is to believe that Allah has the Most Beautiful Names and the Most Exalted Attributes that befit His Greatness and Majesty, without making them resemble the attributes of created beings.
If a particular image comes to a person's mind concerning Allah تعالى, he should not believe that this image represents the reality of Allah. Rather, he should turn away from such imagination and not continue dwelling on it.
The source explains that Allah تعالى is not seen with the physical eyes in this worldly life. Allah سبحانه says:
﴿لَا تُدْرِكُهُ الْأَبْصَارُ﴾
[Al-An'am: 103]
When the Prophet صلى الله عليه وسلم was asked about seeing his Lord, it is reported in Sahih Muslim:
«رأيت نورًا»
And in another narration:
«نورٌ أنَّى أراه؟»
Meaning: How could I see Him?
This is consistent with what Allah تعالى said to Musa عليه السلام:
﴿لَنْ تَرَانِي﴾
[Al-A'raf: 143]
This answer concerns seeing Allah in this worldly life. It does not mean that the vision of Allah تعالى in the Hereafter is denied.
A Muslim believes that the believers will see their Lord in the Hereafter, and this vision is the greatest blessing granted to the people of Paradise.
As for the manner of this vision and the reality of the Essence of Allah سبحانه وتعالى, a human being cannot comprehend them with his intellect, and it is not permissible to attempt to imagine them in the form of any created thing.
A Muslim should turn away from trying to imagine the Essence of Allah تعالى and occupy himself with what benefits him, such as knowing Allah through His Names and Attributes, contemplating His signs, worshipping Him, and obeying Him.
A person should not dwell upon obsessive thoughts that make him search for an image or form of Allah تعالى, because Allah سبحانه وتعالى is far greater than anything the human imagination can encompass.
A Muslim may not imagine Allah تعالى in the form of a human being, light, or any other image, and he is not required in the first place to visualize the Essence of Allah سبحانه.
The obligation is to believe that Allah تعالى is unlike anything else, and that He has the Most Beautiful Names and the Most Exalted Attributes that befit His Majesty, without likening Him to His creation or attempting to determine the manner of His Essence and Attributes.
And Allah knows best.