وَقَالَا: لَا بَأْسَ بِأَنْ يَتَكَلَّمَ مَا لَمْ يَبْدَأْ بِالْخُطْبَةِ.
Translation: Abu Yusuf and Muhammad say there is no objection to speaking until the khutbah begins.
Abu Hanifah links the restraint to the imam’s emergence; his two students link it to the formal start of the sermon. Their difference is about when the prohibition begins, not the duty to listen once the sermon is underway.