✅Answer: Please pay attention to the following narrations:

1 إِسْمَاعِيلَ بْنِ عَبْدالْخَالِقِ قَالَ سَمِعْتُهُ يَقُولُ لَا يَنْبَغِي لِلْإِمَامِ أَنْ يَقُومَ إِذَا صَلَّى حَتَّى يَقْضِيَ كُلُّ مَنْ خَلْفَهُ مَا فَاتَهُ مِنَ الصَّلَاة

📚Al-Tahdhib, Vol. 3, p. 49

Ismail said: 'I heard the Imam (peace be upon him) say: 'It is not fitting for the congregational Imam to get up when he has prayed until all the followers have finished what they missed of the prayer!'

2 عن أَبِي عَبْداللَّه قَالَ: يَنْبَغِي لِلْإِمَامِ أَنْ يَجْلِسَ حَتَّى يُتِمَّ كُلُّ مَنْ خَلْفَهُ صَلَاتَهُمْ

📚Al-Faqih, Vol. 1, p. 400

Imam Sadiq (peace be upon him) said: 'It is fitting for the congregational Imam to sit until all those behind him have finished their prayer!'

3 عَنِ الْحَلَبِيِّ عن أَبِي عَبْداللَّه قال: لَا يَنْبَغِي لِلْإِمَامِ أَنْ یَنْتَقِلَ [یَتَنَفَّل] إِذَا سَلَّمَ حَتَّى يُتِمَّ مَنْ خَلْفَهُ الصَّلَاة

📚Al-Kafi, Vol. 3, p. 341

Imam Sadiq (peace be upon him) said: 'It is not fitting for the congregational Imam to move (or to pray a nafilah) until those behind him have finished the prayer!'

4 عن أَبِي عَبْداللَّه قال: أَيُّمَا رَجُلٍ أَمَّ قَوْماً فَعَلَيْهِ أَنْ يَقْعُدَ بَعْدَ التَّسْلِيمِ وَ لَا يَخْرُجَ مِنْ ذَلِكَ الْمَوْضِعِ حَتَّى يُتِمَّ الَّذِينَ خَلْفَهُ الَّذِينَ سُبِقُوا صَلَاتَهُمْ ذَلِكَ عَلَى كُلِّ إِمَامٍ وَاجِبٌ إِذَا عَلِمَ أَنَّ فِيهِمْ مَسْبُوقاً فَإِنْ عَلِمَ أَنْ لَيْسَ فِيهِمْ مَسْبُوقٌ بِالصَّلَاةِ فَلْيَذْهَبْ حَيْثُ شَاء

📚Al-Kafi, Vol. 3, p. 341

Imam Sadiq (peace be upon him) said: 'Every man who leads a group in prayer, it is his duty to sit after the salam of the prayer and not leave that place until those behind him who were late have finished their prayer. This is obligatory for every congregational Imam if he knows that there are latecomers among them, and if he knows that there are no latecomers from the prayer among them, he can go wherever he wants!'

5 قال أَبُو عَبْداللَّه إِذَا صَلَّيْتَ بِقَوْمٍ فَاقْعُدْ بَعْدَ ما تُسَلِّمُ هُنَيْئَةً

📚Al-Tahdhib, Vol. 3, p. 275

Imam Sadiq (peace be upon him) said: 'When you lead a group in prayer, sit for a little while after you say the salam!'

6 عن سماعة قال: يَنْبَغِي لِلْإِمَامِ أَنْ يَلْبَثَ قَبْلَ أَنْ يُكَلِّمَ أَحَداً حَتَّى يَرَى أَنَّ مَنْ خَلْفَهُ قَدْ أَتَمُّوا الصَّلَاةَ ثُمَّ يَنْصَرِفُ هُو

📚Al-Tahdhib, Vol. 2, p. 104

Sam'ah said: 'The Imam (peace be upon him) said: 'It is fitting for the congregational Imam to remain before he speaks to anyone until he sees that the followers have finished the prayer, and then he may go!'

7 عَلِيِّ بْنِ جَعْفَرٍ عَنْ أَخِيهِ مُوسَى بْنِ جَعْفَرٍ قَالَ: سَأَلْتُهُ عَنْ حَدِّ قُعُودِ الْإِمَامِ بَعْدَ التَّسْلِيمِ مَا هُوَ قَالَ يُسَلِّمُ وَ لَا يَنْصَرِفُ وَ لَا يَلْتَفِتُ حَتَّى يَعْلَمَ أَنَّ كُلَّ مَنْ دَخَلَ مَعَهُ فِي صَلَاتِهِ قَدْ أَتَمَّ صَلَاتَهُ ثُمَّ يَنْصَرِفُ

📚Qurb al-Isnad, p. 96

Ali ibn Ja'far said: 'I asked Musa ibn Ja'far (peace be upon him) about the limit of the Imam's sitting after the salam. He said: 'He says the salam and does not move until he knows that all those who joined his prayer have finished their prayer, then he leaves!'

8 عن عَمَّارٍ قَالَ: سَأَلْتُ أَبَا عَبْداللَّه عَنِ الرَّجُلِ يُصَلِّي بِقَوْمٍ فَيَدْخُلُ قَوْمٌ فِي صَلَاتِهِ بِقَدْرِ مَا قَدْ صَلَّى رَكْعَةً أَوْ أَكْثَرَ مِنْ ذَلِكَ فَإِذَا فَرَغَ مِنْ صَلَاتِهِ وَ سَلَّمَ أَ يَجُوزُ لَهُ وَ هُوَ إِمَامٌ أَنْ يَقُومَ مِنْ مَوْضِعِهِ قَبْلَ أَنْ يَفْرُغَ مَنْ دَخَلَ فِي صَلَاتِهِ قَالَ نَعَمْ

📚Al-Tahdhib, Vol. 3, p. 273

Ammar said: 'I asked Imam Sadiq (peace be upon him) about a person who leads a congregation in prayer and a group joins his prayer for one rak'ah or more. When he is finished with his prayer and has said the salam, is it permissible for him as the Imam to get up from his place before those who joined his prayer have finished?' He said: 'Yes!'

✅According to the above narrations and others, the congregational Imam is obligated to sit in his place after the salam of the prayer and not get up until all those who have not caught up with one or more rak'ahs have finished their prayer.

✅Of course, in hadith 8️⃣ from Ammar al-Sabati, an exception to this has been narrated, but considering the many other narrations and their emphasis, especially narration 4️⃣, it is fitting that this act not be abandoned by the congregational Imam.