The philosophy of Wahdat al-Wujud was first ever prevailed by Husayn ibn Ali in his book Mirat-ul-Arifeen which he wrote in response to the question of his son Zayn al-Abidin about the explanation of Surah Al-Fatiha.
In this book, he interpreted the ideology of Wahdat al-wujud for the first time in the most comprehensive way.
Hence, in a secondary meaning, the term wujūd is used as shorthand to refer to the whole cosmos, to everything that exists.
This methodology was given a name of tashkik al-wujud and it thus explains that there is gradation of existence that stand in a vast hierarchical chain of being (marāṭib al-wujūd) from floor (farsh) to divine throne (ʿarsh), but the wujūd of each existent māhīyya is nothing but a grade of the single reality of wujūd whose source is God, the absolute being (al-wujūd al-mutlaq).
Rather, the things borrow wujud from God, much as the earth borrow light from the sun.
The issue is how wujūd can rightfully be attributed to the things, also called "entities" (aʿyān).
The following gives details about his vision of creation in three stages: the Most Holy Effusion (al-fayd al-aqdas), the Holy Effusion (al-fayd al-muqaddas) and the Perpetual Effusion (al-fayd al-mustamirr).
Sachal Sarmast and Bulleh Shah two Sufi poets from India, were also ardent followers of Waḥdat al-wujūd.Ibn 'Arabî used the term "effusion" (fayd) to denote the act of creation.His writings contain expressions which show different stages of creation, a distinction merely logical and not actual.Wujūd is the absolute, infinite, nondelimited reality of God, while all others remain relative, finite, and delimited".