Sayyidah Aishah Siddiqah (may Allah be pleased with her) narrated that the Prophet (peace and blessings be upon him) said: "Two snakes are sent upon the disbeliever, one from the side of his head and the other from the side of his feet. They both sting him, and whenever they finish, they begin again, and this will continue until the Day of Resurrection."
Ahmad recorded it, and its chain is hasan (good).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الجنائز / 4284