Wujūd (existence, finding) is essentially Allah's wujūd (which is the necessary wujūd without which nothing else would exist at all), whereas the wujūd (existence) of creation or of the contingent entities like human beings, angels etc. is a very limited and defined or a metaphorical*, 'borrowed' wujūd, so it is really necessary to distinguish between Wujūd Mutlaq (absolute existence) and wujūd mustafād (borrowed existence).
Then it can be seen that from our human perspective we are held to affirm:
- on the one hand the absolute unlikeliness of Allah with anything created, called tanzīh or transcendence of God, (in Western metaphysics, where the concept of 'transcendence' is not as clear and consistent as in Islam, it gave rise to serious misconceptions) and
- on the other hand the likeness of Allah with creation, tashbīh. I.e. creation is manifestation, it is the "place of the Theophany"** where Allah makes Himself be known: as Allah says in a hadith qudsī:
"I was a Treasure unknown then I desired to be known so I created a creation to which I made Myself known, then they knew Me." .
This means man can conceive at least something of Allah's names or qualities.
For example Prophet Muhammad ﷺ peace and blessings of Allah be upon him) told his Companions the story of the bird mother and her extent of mercy and compassion for her young ones. By drawing this example from the world, ie. from their human experience, they were reminded of the universal concept of mercy. At the same time this mercy "in the worldly realm" is only a trace of the vast Divine mercy and compassion (rahma), which sooner or later will overcome all negativity in created beings.
As Allah says in another hadith qudsī:
"Truly My Compassion supercedes my wrath"
4.) Both Aspects
So concerning imān and ʿilm one has to observe those two aspects of tanzīh and tashbīh and it is not possible to prefer the one aspect over the other when referring to Allah in His Divine function (al-Ulūhiyyah).
In other words, both aspects of the Divine must be simultaneously affirmed or, at a more fundamental level, intuited, so that relativity or delimited reality is seen as an intrinsic dimension of absoluteness.
5.) ”Oneness of being” A Term Not Used
It seems that Shaykh Muhyi-Dīn Ibn ʿArabi never used the notion of 'wahdat-ul wujūd' (oneness of being or existence) himself, it was used by those who came after him, f ex Al-Kashāni. The concept can be ambiguous, and therefore misleading. Instead Shaykh Muhyi-Dīn Ibn ʿArabi used the notion of “ʿain al-wujūd” (essence of existence). As it is these are all different terms of one reality, and it is our duty as muslims to realize the meaning of it, so as not to fall from the straight path of tawhīd .
So wahdat-ul wujūd is really ʿain al wujūd, and it is formalized in the first part of the shahādah, which states that in essence nothing really exists except the Real (Allah), because everything else has only a limited, defined, metaphorical*, borrowed wujūd.
And Allah knows best and most.
* metaphorical: expressing one thing in terms normally denoting another.
** manifestation: the recurrence of the creative act: tajrīd-ul khalq
 A discussion of the 'Treasure-hadith' is here: [link]
 From: Paths to Transcendence, Reza Shah-Kazemi
Islamic Glossary: < wujūd >
"In any case, what Westerners call civilization, the others would call barbarity, because it is precisely lacking in the essential, that is to say, a principle of a higher order."
René Guénon, East And West, 1924
صلّى الله على سيّدنا محمّد و على آله و صحبه و سلّم
The blessings and peace of Allah on the Prophet, his Family, and his Companions, ( sallAllahu `aleihi wa sallam ) .
Ibn ʿArabi - Texts Overview