Musnad Ahmad 33:622

Musa and Hasan narrated to us, they said: Ibn Lahi'ah narrated to us. Hasan said in his narration: Abu al-Zubayr narrated to us. And Musa said: From Abu al-Zubayr, that he asked Jabir about the *maytharah* (saddle cushion) — the purple one. Jabir said: The Prophet, may Allah bless him and grant him peace, said: "I do not ride upon it, nor do I wear a shirt hemmed with silk, nor do I wear *al-Qassi* (a type of silk-blend garment)."