Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: A man killed his slave woman, who had borne him a child, because she reviled the Prophet (peace and blessings be upon him), and the Prophet (peace and blessings be upon him) declared her blood to be unavenged.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المرتد / 16863