It is narrated from one of the purified wives of the Prophet (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) said: Whoever goes to a soothsayer (fortune-teller) and confirms what he says, his prayer will not be accepted for forty days.
Hadith Referenceمسند احمد / مسند المدنيين رضي الله عنهم اجمعين / 16638