وَيُكْرَهُ أَنْ يَتَنَفَّلَ بَعْدَ صَلَاةِ الْفَجْرِ حَتَّى تَطْلُعَ الشَّمْسُ،
Translation: Voluntary prayer is disliked after the Fajr prayer until the sun rises.
After the Fajr obligatory prayer, voluntary prayer is disliked until sunrise. The actual sunrise interval is subject to an even stronger prohibition.