Tahalli (emptying, becoming vacant) is to turn away from everything that causes occupation, whether outward or inward. This includes choosing khalwa (seclusion), preferring uzla (retreat), and adhering to wahda (solitude). (Luma, 440)
Tehalli (adopting a state, adorning oneself) is to affiliate oneself (intisāb) with a group worthy of praise in word and deed. (Hujwīrī, 471)
Tahalli is the servant turning away from occupations that distract from Allah. Foremost among these are the occupations of dunyā (the worldly life). In this respect, tahalli—when it comes from Allah by means of ināya (divine favor)—is for one's hand to be empty of worldly possessions. The second type of tahalli is to empty the qalb (the heart) of desire for the hereafter. Thirdly, it is to empty the sirr (the innermost self) of following caprice. Fourthly, it is to turn away from companionship with people and to empty the heart of thinking about them. (Hujwīrī, 472)
Tahalli is to prefer khalwa (seclusion) by turning away from everything that separates you from the Real (al-Ḥaqq). (Istilāh, 534)
Tehalli is to adorn oneself with the ethics of servanthood. This is the correct understanding. As long as the Real is kept distinct from the servant, this is the best definition. (Istilāh, 541)
According to the community of Sufis, tehalli is to strive to resemble the states of the truthful (ṣādiqūn) in word and deed. In our view, such a person is truthful in their spiritual journey (sayr sulūk) because they have been affected by the divine names. From the states of tehalli of the truthful, it is necessary to understand that which they have truly internalized. When they are adorned with qualities not their own, they have donned the garment of taqlid (imitation), or they have adopted states that are truly theirs; thus, they are among the truthful.
In our view, tehalli, according to the difficulty of its discernment, is to adorn oneself with the divine names within the bounds of what is permitted. Bilqis, regarding her throne, doubted because of the distance and said, "It is as though it is it," but had she witnessed (shāhid) the divine action, she would have known without doubt that it was her throne. Thus are they.