آنَسَتْ نَبْأَةً وَأَفْزَعَهَا الْقُنَّاصُ ۞ عَصْرًا وَقَدْ دَنَا الْإِمْسَاءُ
Translation: The female ostrich detected a sound; hunters frightened her late in the day as evening drew near.
Nabʾah is a slight sound or signal, while al-qunnāṣ are hunters. ʿAṣran refers to the late part of the day, and danā al-imsāʾu states that evening was approaching.
The verse now supplies a cause for speed: the bird senses danger and responds. What began as a static simile becomes a short narrative sequence.