Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: "Whoever goes to a soothsayer, a sorcerer, or one who claims knowledge of the unseen, and believes him, has disbelieved in the Shari'ah of Muhammad (peace and blessings be upon him)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب القسامة / 16497