Bilal made the call to prayer before dawn broke, so the Prophet ﷺ ordered him to go back and announce, "The servant has slept! The servant has slept!"Musa added in his version, "So he went back and announced, 'The servant has slept!'"
حدثنا موسى بن إسمعيل وداود بن شبيب المعنى قالا حدثنا حماد عن أيوب عن نافع
أن بلالا أذن قبل طلوع الفجر فأمره النبي ﷺ أن يرجع فينادي ألا إن العبد قد نام ألا إن العبد قد نام زاد موسى فرجع فنادى ألا إن العبد قد نام
No references are available.
[Hasan] Abd bin Humayd narrated it, no. 782, and others, from the hadith of Hammad bin Salama, with this wording. Tirmidhi mentioned it without a full chain, no. 203. The hadith has supporting narrations in Bayhaqi, 1/383, and elsewhere, as I have established in Anwar al-Sunan fi Tahqiq Athar al-Sunan, no. 261.