English translation
[2535] 35 - (...) It was narrated that Sahl bin Sa'd [may Allâh be pleased with him] said: "When this verse was revealed - "And eat and drink until the white thread appears to you distinct from the black thread"[2] - if a man wanted to fast, he would tie a white thread to one foot and a black thread to the other, then he would carry on eating and drinking until he could tell them apart when he saw them. Then after that, Allâh revealed: "of dawn" then they realized that what was meant by that was night and day."
