Sayyiduna Ali (may Allah be pleased with him) said concerning two slave-women who are sisters: One verse makes them both lawful while another verse makes them forbidden. He said: I neither command nor forbid, I neither declare lawful nor declare forbidden, and I do not do it, nor has anyone of my family done it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13935