Adi reported,

Adi took a white cord and a black cord, and during part of the night he looked at them but could not distinguish between them. In the morning, he said, "Messenger of Allah, I placed two cords under my pillow."The Prophet ﷺ replied, "Your pillow must be very wide indeed if the white thread and the black thread fit beneath it."

Bukhari 4509

Sahih

حدثنا موسى بن إسماعيل حدثنا أبو عوانة عن حصين عن الشعبي

عن عدي قال

أخذ عدي عقالا أبيض وعقالا أسود حتى كان بعض الليل نظر فلم يستبينا فلما أصبح قال يا رسول الله جعلت تحت وسادي عقالين قال إن وسادك إذا لعريض أن كان الخيط الأبيض والأسود تحت وسادتك

البخاري 4509صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Bukhari
Book
Tafsir
Chapter
His saying, "And eat and drink until the white thread of dawn becomes distinct to you from the black thread of Fajr. Then complete the fast until night, and do not have relations with them while you are secluded in the mosques"
Numbering
Darussalam 4509
Bukhari 4509