Musannaf Ibn Abi Shayba 33:244

Yazid ibn Harun narrated to us, he said: Ashras Abu Shayban narrated to us, he said: ‘Ata’ al-Khurasani narrated to us, he said: ‘Umar ibn al-Khattab was delayed from his companions, so he came out to them in the evening. They said: "What delayed you?" He said: "I washed my clothes, and when they dried, I came out to you."