Sayyiduna Abu Hurayrah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "The price of a dog, the fee of a soothsayer and the earnings of a prostitute are not lawful."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11010