She had performed the pilgrimage with the Prophet ﷺ. She said, the Messenger of Allah ﷺ used to say, "Ibn Umm Maktum calls the adhan at night, so eat and drink until Bilal calls the adhan," or, "Bilal calls the adhan at night, so eat and drink until Ibn Umm Maktum calls the adhan." One of them would be ascending while the other was descending, and we would cling to him and say, "Stay where you are until we finish our suhoor."
حدثنا عفان حدثنا شعبة
وكانت حجت مع النبي ﷺ قالت كان رسول الله ﷺ يقول إن ابن أم مكتوم ينادي بليل فكلوا واشربوا حتى ينادي بلال أو إن بلالا ينادي بليل فكلوا واشربوا حتى ينادي ابن أم مكتوم وكان يصعد هذا وينزل هذا فنتعلق به فنقول كما أنت حتى نتسحر
Its isnad is sahih. Khubayb bin Abdul-Rahman al-Ansari is among the trustworthy narrators of the Tabiin, and his hadith is found in the collections of the Jamaah. Imam Ahmad will mention the disagreement among the narrators regarding it, and the correct version is that Bilal used to give the call to prayer while it was still night. See 24154.