Abu Uthman narrates from Sayyiduna Salman (may Allah be pleased with him) (I think he narrated it as marfu'): "Allah made the lawful lawful and the unlawful unlawful. What He made lawful is lawful, what He made unlawful is unlawful, and what He kept silent about is permissible."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19722