Al-Nasāʾī narrates—on the authority of Abū Hurayrah—: “Whoever ties a knot and then blows into it has practiced sorcery; whoever practices sorcery has committed polytheism; and whoever fastens his heart to something will be left to it.” (1)

‘Whoever ties a knot’: this refers to the way sorcerers twist threads and the like.
‘and blows into it’: nafth is blowing mixed with a trace of saliva, lighter than spitting.
‘has practiced sorcery’: that is, he has carried out the forbidden act of magic.
‘and whoever practices sorcery has committed polytheism’: because magic cannot be worked without an element of shirk; it relies on seeking help from the devils.
‘and whoever fastens his heart to something will be left to it’: meaning, if a person’s heart attaches to an object and he depends on it, Allah will leave him to that object and forsake him.

Overall meaning of the ḥadīth: The Prophet ﷺ identifies a particular form of sorcery, states its ruling, and warns his community against it. He explains that among the kinds of magic is to tie knots in threads and similar materials and then blow into those knots with breath moistened by saliva. When sorcerers wish to cast a spell, they tie the threads and blow on every knot so the sorcery they desire may take effect; their evil souls become attuned to malice, they seek aid from the devils, and they blow into those knots, so from that vile soul there issues a breath coupled