Musnad Ahmad 658:196

Waki’ narrated to us, Sufyan narrated to us, from Abu Ishaq, from Al-Bara’ who said: A silk garment was brought to the Prophet, may Allah bless him and grant him peace, and his companions began to marvel at its softness. The Messenger of Allah, may Allah bless him and grant him peace, said: "The handkerchiefs of Sa’d ibn Mu’adh in Paradise are softer than this."