And if they posit it as existing in external reality, they make it a part of existing beings. The Creator would then be part of the created being, or an accident inhering in it. All of this is self-evidently false, and it has been discussed at length elsewhere.

As for his contradiction, his words:

“You have never been absent from my heart or my eye;
Between you and us there is no separation”

imply a distinction: the one addressed is other than the speaker, and the speaker has an eye and a heart from which the one addressed is never absent. Rather, the heart and eye witness him, and the witness is other than what is witnessed.

His words:

“Between you and us there is no separation”

affirm both a first-person pronoun and a second-person pronoun, thereby affirming two distinct beings. If they say, “These are loci of manifestation and self-disclosure,” the reply is: if the loci of manifestation and self-disclosure are other than the one who manifests and discloses himself, then duality is established and unity disproved. If he is identical with them, then multiplicity is disproved. Combining the two is a contradiction.

As for the words:

“Abandon the wrongdoing of your natural disposition and be united with Allah …
Otherwise, all your claims are untenable”—

if the speaker means unrestricted union, then the one who parts is identical with what he parts from: he is the natural disposition and its wrongdoing. He is also the one addressed by the words, “and be united with Allah,” and by the words, “all your claims are untenable.” He is, moreover, the one uttering these words. The contradiction in this is plain.