أُسْنِدَ إِلَيْهِ — Translation: “is attributed to it.”
إسناد means linking an action or predication to a noun in the sentence. In قَامَ زَيْدٌ, standing is attributed to Zayd. In زَيْدٌ ضَارِبٌ أَبُوهُ عَمْرًا, the striking is attributed not to Zayd but to his father, أَبُوهُ; Zayd is the mubtadaʾ.