Shaykh Ahmad was influenced by mythologies

The other symbol to which Shaykh Ahmad appeals in this treatise is more obviously a "cosmic reality", a natural phenomenon that, as Ricoeur has said, both manifests and signifies higher realities. The world-tree, a powerful mythological image in many cultures, has especial resonances for mystics in the world religions, for it immediately suggests the spanning of earth and sky; more, it speaks of development, of the growth of a towering complex being from a tiny kernel. The Indo-European root deru is the origin of both the English word "tree" and the word "true". "Druid", the name for holy men in Celtic Europe, means the "knower of the tree (or the true)" (deru-wid). In ancient Iranian mythology, preserved in Zoroastrian texts, the Saena tree that stood in the midst of the cosmic Lake Vourukasha was said to be the source of all seeds. In this fabulous Tree of Healing (vispobish) nested the Saena bird, with the head of a dog and the body of a fowl, which from time to time flapped its enormous wings, sending the multifarious seeds of the Saena tree flying over the earth, upon which they landed and from which they grew into the vegetation that covered it. In Islamic mysticism, many elements of this myth were taken over. The Saena bird, for instance, became for Suhrawardi and Faridu'd-Din 'Attar (d. ca. 1230) the "Simurgh" (a contraction of Saena meregh), and they see it as symbol of the soul's mystical unity with God. It is said that its haunt is the mystical mountain of Qaf (a transformation of an Iranian mythic geographical symbol) beyond the world-sea (i.e. Vourukasha). Kazem Tehrani has pointed out that for Suhrawardi, the tree of all seeds is associated with a return of the soul to the "first form" (shakl-i avval), identified with the nest of the Simurgh, a conception that differs slightly from 'Attar's notion of the mythical bird as a mirror in which the soul sees itself. The Iranian idea of the Saena tree was probably mediated to Shaykh Ahmad through writings of such Iranian mystics, and it has for him, as well, connotations of the soul's return to its primal, pure estate.

(Juan R. I. Cole, The World as Text: Cosmologies of Shaykh Ahmad al-Ahsa'i, Studia Islamica No. 80 (1994), pp. 145-163 Published By Brill)