It is narrated from Sayyiduna Zayd bin Arqam (may Allah be pleased with him); he said: A man used to visit the Prophet (peace and blessings be upon him) frequently. He tied some knots (of magic) against him (peace and blessings be upon him) and threw them into the well of a man from the Ansar. Then two angels came to visit him (peace and blessings be upon him) in his illness; one of them sat by his (peace and blessings be upon him) head and the other by his (peace and blessings be upon him) feet. One asked the other: "Do you know what his illness is?" The other said: "So-and-so, who visits him, tied some knots against him and threw them into the well of so-and-so the Ansari. If a man were sent and took out the knots, he would find the water turned yellow." (The narrator says:) So he (peace and blessings be upon him) sent a man, who took out the knots and untied them, and he (peace and blessings be upon him) recovered. After that the man continued to visit the Prophet (peace and blessings be upon him), but he (peace and blessings be upon him) never even mentioned it to him nor reproached him.
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4992