its usual time is not to be taken at face value, for this very wording continues: “then he prayed Fajr when dawn had broken.”
Likewise, Jābir says in his lengthy ḥadīth, “and he performed Fajr when the dawn was plainly visible to him,” a report related by Muslim and others.
What is meant, then, is that the Prophet prayed Fajr earlier than the time to which people were accustomed—that is, he prayed it in such deep darkness that some of them were still uncertain whether dawn had actually come.
For this reason al-Ḥāfiẓ Ibn Ḥajar states in Fatḥ al-Bārī (3/413):
“Nothing in this narration supports those who object to praying Fajr while it is still dark, for it is firmly established from ʿĀʾishah and others that he used to pray it in darkness. What is intended here is that when the muʿadhdhin informed him that dawn had risen, he would pray the two sunnah units of Fajr in his house, then come out and lead the obligatory Ṣubḥ prayer while it was still dark. At Muzdalifah, however, the people were already assembled and the dawn was right before their eyes, so they hastened to the prayer the moment its light appeared—indeed, some of them had not yet realized that dawn had broken, as the second narration makes clear.”
1 – When it is the practice of the rulers or imams to delay a prayer beyond its optimal time, the Muslim should perform that prayer at its prescribed time in his own home, then pray it again with them whenever they perform it; the second performance counts as a voluntary prayer for him.
Abū Dharr – may Allah be pleased with him – reported that the Messenger of Allah ﷺ said to him, “How will you be when governors are set over you who delay the prayer from its appointed time, or even let the prayer die outside its time?” I asked, “What do you command me to do?” He replied, “Pray the prayer at its proper time; then, if you catch it with them, pray with them as well, and it will be a voluntary prayer for you.”