Praise be to Allah,
Ismaa’ eel ibn Ibraaheern ibn ‘Ulayyah narrated to us from Humayd [at-Taweel] from Anas ibn Maalik who said,
“Allah’s Messenger (PBUH) was asked about the time of the Fajr prayer, so he commanded Bilaal [ibn Rabaah] when dawn had just broken to call the iqamah for prayer. On the following day, he waited until it became brighter, then he (PBUH) asked, ‘Where is the man who was asking about the time for the Fajr prayer? Its time falls between these two [extremes].”‘
(Musnad Ahmad, Vol. 3, p. 113. The isnaad of this Hadeeth is Saheeh according to the conditions set by al-Bukhaaree and Muslim.)
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Source:
Thulaathiyyaat Musnad Ahmad ibn Hanbal (may Allah have mercy on him)
Reports of Imaam Ahmad that have only three narrators between him and the Prophet, peace, and blessings be upon him.
Shaykh Muhammad ibn Ahmad ibn Saalim as–Saffaareenee al–Hanbalee ~(1114 –1188 AH)