Is the name Zaahir one of the names of Allah?

It is well established that the names and attributes of Allah
are a matter that is limited to what is mentioned in the Qur’aan and Sunnah,
i.e., they can only be known from the Islamic texts that mentioned them, and
there is no room in this matter for ijtihaad  or qiyaas (analogy) or
istihsaan (personal view). 

Imam Ahmad (may Allah have mercy on him) said: Allah cannot
be described except in the terms in which He described Himself or His
Messenger described Him, and that cannot go beyond what is mentioned in the
Qur’aan and hadeeth. 

End quote from Majmoo‘ al-Fataawa, 5/26 

Al-Khaazin said in his Tafseer (3/136): 

The words of Allah (interpretation of the meaning): “so
call on Him by them” [Ghaafir 40:65] means: call upon Allah
by His names by which He
called Himself or His Messenger called him. This indicates that the names of
Allah, may He be exalted, are are matter to be based solely on the texts of
the Qur’aan and saheeh hadeeths with no room for human opinion. What
indicates that this opinion is correct and supports it is the fact that it
is permissible to say Ya Jawaad but it is not permissible to say Ya Sakhi
(even though both mean the same, i.e. Generous); and it is permissible to
say Ya ‘Aalim but it is not permissible to say Ya ‘Aaqil (even though both
mean knowing). End quote. 

Any names or attributes of Allah
that are not mentioned in the Qur’aan or Sunnah cannot be known by any
means, because knowledge of the names and attributes of Allah is restricted
to what is mentioned in them (the Qur’aan and Sunnah), and whatever we have
no knowledge of, we leave the knowledge thereof to the One Who knows it, as
in the du‘aa’ for relief from distress: “…
as’aluka bi kulli ismin huwa laka sammayta bihi nafsaka aw anzaltahu fi
kitaabika aw ‘allamtahu ahadan min khalqika aw ista’tharta bihi fi ‘ilm
il-ghaybi ‘andaka … (… I ask You by every Name
belonging to You which You named Yourself with, or revealed in Your Book, or
You taught to any of Your creation, or You have preserved in the knowledge
of the unseen with You…).”
Narrated by Ahmad, 3704; classed as saheeh by al-Albaani in al-Saheehah,
199 

Ibn al-Qayyim (may Allah have
mercy on him) said: 

This indicates that Allah, may He
be glorified and exalted, has names and attributes that He has preserved in
the knowledge of the unseen with Him to the exclusion of His creation; they
are not known to any angel who is close to Him or any Prophet who was sent.
It is sufficient for us to admit our helplessness and stop at the limit of
what has been permitted to us concerning that. So we should neither go to
extremes concerning it nor ignore the issue altogether. End quote. 

Badaa’i‘ al-Fawaa’id,
2/413 

Thus it becomes clear that
ascribing to Allah the name mentioned, Zaahir, or any other name that is not
mentioned in an Islamic text, is overstepping the permitted limit and
speaking about Allah, may He be exalted, without knowledge. 

Shaykh Ibn ‘Uthaymeen (may Allah
have mercy on him) said: 

It is not permissible to ascribe
any name or attribute to Allah, may He be exalted, that is not mentioned in
the Qur’aan or Sunnah, because that is speaking about Allah, may He be
exalted, without knowledge, and Allah says (interpretation of the meaning): 

“Say (O Muhammad SAW): (But)
the things that my Lord has indeed forbidden are Al-Fawâhish (great evil
sins, every kind of unlawful sexual intercourse,) whether committed openly
or secretly, sins (of all kinds), unrighteous oppression, joining partners
(in worship) with Allâh for which He has given no authority, and saying
things about Allâh of which you have no knowledge”

[al-A ‘raaf 7:33]

“And follow not (O man i.e.,
say not, or do not or witness not) that of which you have no knowledge.
Verily! The hearing, and the sight, and the heart, of each of those one will
be questioned (by Allah)”

[al-Isra’ 17:36]. 

End quote from Majmoo‘ Fataawa
wa Rasaa’il Ibn ‘Uthaymeen, 4/230 

And Allah knows best 

For more information please see
the answer to question no. 48964.