Fulfillment of vows and promises

يُوفُونَ بِٱلنَّذْرِ وَيَخَافُونَ يَوْمًا كَانَ شَرُّهُۥ مُسْتَطِيرًا

They [are those who] fulfill [their] vows and fear a Day whose evil will be widespread.