The Prophet ﷺ said, "Bilal calls the adhan at night, so eat and drink until Ibn Umm Maktum calls the adhan."She said, "I do not recall it being more than the time it took for one to come down and the other to go up."
حدثنا يحيى عن عبيد الله قال سمعت القاسم
عن النبي ﷺ إن بلالا يؤذن بليل فكلوا واشربوا حتى يؤذن ابن أم مكتوم قالت فلا أعلمه إلا كان قدر ما ينزل هذا ويرقى هذا
Its isnad is sahih, all its men are found in the six major collections and are among the great hadith scholars. Yahya is Ibn Saeed Qattan, Ubaydullah is Ibn Umar Umari, and Qasim is Ibn Muhammad bin Abu Bakr.The hadith was reported by Bukhari 1/160 (Shab edition), Muslim 2/768 no. 1092, Tirmidhi 3/77 no. 706, who graded it hasan, and Ibn Khuzayma 3/211 no. 1932, all of them in the chapter on fasting.