Musannaf Ibn Abi Shayba 36:264

Waki' narrated to us, from Sufyan, from Abu Ishaq, from al-Bara', who said: A silk garment was gifted to the Prophet, may God bless him and grant him peace, and they began to marvel at its softness. The Prophet, may God bless him and grant him peace, said: "The handkerchiefs of Sa'd in Paradise are softer than what you see."