It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever ties a knot and then blows into it has certainly practised magic, and whoever practises magic has committed shirk (associated partners with Allah), and whoever hangs up something (for protection) will be entrusted to it."
Imam al-Tabarani (may Allah have mercy on him) said: "No one narrated this hadith from Abbad except Abu Dawud."
Hadith Referenceالمعجم الأوسط / باب الألف / 1469
Hadith Takhrij«أخرجه النسائي فى «المجتبى» برقم: 4090 / 1، والنسائي فى «السنن الكبرى» برقم: 3528»