أَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، قَالَ حَدَّثَنَا أَبُو دَاوُدَ، قَالَ حَدَّثَنَا عَبَّادُ بْنُ مَيْسَرَةَ الْمِنْقَرِيُّ، عَنِ الْحَسَنِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ مَنْ عَقَدَ عُقْدَةً ثُمَّ نَفَثَ فِيهَا فَقَدْ سَحَرَ وَمَنْ سَحَرَ فَقَدْ أَشْرَكَ وَمَنْ تَعَلَّقَ شَيْئًا وُكِّلَ إِلَيْهِ ‏"‏ ‏.‏

It was narrated that Abu Hurairah said: "The Messenger of Allah [SAW] said: 'Whoever ties a know and blows on it, he has practiced magic; and whoever practices magic, he has committed Shirk; and whoever hangs up something (as an amulet) will be entrusted to it.'" Translation Not Available

Book Ref: Sunan An Nisai Book 37 Hadith 4079
Web Ref:  Sunan An Nisai Vol 5 Book 37 Hadith 4084