Ayesha reported,

Bilal used to give the call to prayer at night, so the Messenger of Allah ﷺ said, "Eat and drink until Ibn Umm Maktum gives the call, for he does not call until dawn breaks."Qasim said, "There was nothing between their two calls except that one would descend and the other would ascend."

Azami 4362

Sahih

عن عائشة

أن بلالا كان يؤذن بليل، فقال رسول الله ﷺ: كلوا واشربوا حتى يؤذن ابن أم مكتوم، فإنه لا يؤذن حتى يطلع الفجر. قال القاسم: ولم يكن بين أذانهما إلا أن يرقى ذا وينزل ذا.

الأعظمي 4362صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Fasting
Chapter
Obligation of fasting, its virtue, and its rulings
Section
Recommendation to delay suhoor until the true Fajr becomes apparent
Numbering
Jami al-Kamil 4362 (2nd edition)
Azami 4362