Musnad Ahmad 658:213

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from Abu Ishaq, who said: I heard al-Bara’ saying: A silk garment was gifted to the Messenger of Allah, may Allah bless him and grant him peace. His companions began touching it and marveling at its softness. He said: "Do you marvel at the softness of this? The handkerchiefs of Sa‘d ibn Mu‘adh in Paradise are better than it, or softer."