"[We would have seized him by the right hand]," meaning: with the right, as a punishment. Al-Hasan’s interpretation is: he says, we would have cut off his right hand.
﴿لأخذنا مِنْهُ بِالْيَمِينِ﴾ أَيْ: بِالْحَقِّ عُقُوبَةٌ، وَتَفْسِيرُ الْحَسَنِ: يَقُول: لقطعنا يَده الْيُمْنَى
