It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) "forbade the earnings from a dog and the earnings of a singing woman."
The Shaykh (may Allah have mercy on him) said: It is possible that he forbade earnings about which it is not known where they earned them from, out of fear of falling into what is unlawful.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الإجارة / 11688