✅ Answer: Please refer to the following narrations:

1⃣مُعَاوِيَةَ بْنِ عَمَّارٍ عَنْ أَبِي عَبْداللَّه قَالَ: تُكَبِّرُ لَيْلَةَ الْفِطْرِ وَ صَبِيحَةَ الْفِطْرِ كَمَا تُكَبِّرُ فِي الْعَشْرِ

📚 Al-Kafi, vol. 4, p. 167

Imam Sadiq, peace be upon him, said: 'On the night and morning of Eid al-Fitr, you say the Takbir, just as you do on the day of Eid al-Adha.'

2⃣عَنْ سَعِيدٍ النَّقَّاشِ قَالَ: قَالَ أَبُو عَبْداللَّه لِي أَمَا إِنَّ فِي الْفِطْرِ تَكْبِيراً وَ لَكِنَّهُ مَسْتور قَالَ قُلْتُ: وَ أَيْنَ هُوَ قَالَ فِي لَيْلَةِ الْفِطْرِ- فِي الْمَغْرِبِ وَ الْعِشَاءِ الْآخِرَةِ وَ فِي صَلَاةِ الْفَجْرِ وَ فِي صَلَاةِ الْعِيدِ ثُمَّ يَقْطَعُ قَالَ قُلْتُ: كَيْفَ أَقُولُ: قَالَ تَقُولُ اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ لَا إِلَهَ إِلَّا اللَّهُ وَ اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ وَ لِلَّهِ الْحَمْدُ اللَّهُ أَكْبَرُ عَلَى مَا هَدَانَا- وَ هُوَ

قَوْلُ اللَّهِ عَزَّ وَ جَلَّ وَ لِتُكْمِلُوا الْعِدَّةَ يَعْنِي الصِّيَامَ وَ لِتُكَبِّرُوا اللَّهَ عَلى ما هَداكُمْ

📚 Al-Kafi, vol. 4, p. 166

Saeed Naqqash said: Imam Sadiq, peace be upon him, told me: 'Know that there is a hidden Takbir on Eid al-Fitr!'

He said: 'I asked: Where is it?' The Imam replied: 'It is after the Maghrib prayer on the night of Eid al-Fitr, after the Isha prayer, after the Fajr prayer, and after the Eid prayer, then it is stopped!'

He said: 'I asked: How should I say it?' The Imam replied: 'You should say:'

اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ لَا إِلَهَ إِلَّا اللَّهُ وَ اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ وَ لِلَّهِ الْحَمْدُ اللَّهُ أَكْبَرُ عَلَى مَا هَدَانَا

This is the saying of Allah, the Almighty, in Surah Al-Baqarah, verse 185: 'So that you complete the number and say Takbir of Allah for what He has guided you!'

3⃣الْفضل بْنِ شَاذَانَ عَنِ الرِّضَا أَنَّهُ كَتَبَ إِلَى الْمَأْمُونِ وَ التَّكْبِيرُ فِي الْعِيدَيْنِ وَاجِبٌ فِي الْفِطْرِ فِي دُبُرِ خَمْسِ صَلَوَاتٍ وَ يُبْدَأُ بِهِ فِي دُبُرِ صَلَاةِ الْمَغْرِبِ لَيْلَةَ الْفِطْر

📚 Uyun Akhbar al-Ridha, vol. 2, p. 125

Imam Ridha, peace be upon him, wrote to Ma'mun: 'The Takbir on Eid al-Fitr and Eid al-Adha is obligatory. On Eid al-Fitr, it is after five prayers, starting from Maghrib on the night of Eid al-Fitr...'

4⃣ Al-A’mash from Ja’far ibn Muhammad in the narration of Sharai’ al-Din said: 'The Takbir on the two Eids is obligatory. As for Eid al-Fitr, it is during five prayers, starting from the Maghrib prayer on the night of Eid al-Fitr until the Asr prayer on the day of Eid al-Fitr. It should be said: Allahu Akbar, Allahu Akbar, La ilaha illallah, Allahu Akbar, wa lillahi al-hamd, Allahu Akbar, ‘ala ma hadana, wa al-hamdu lillah ‘ala ma ablaana.’' This is due to Allah's saying: 'So that you complete the number and say Takbir to Allah for what He has guided you.'

📚 Khesal, p. 609

In the narration of Sharai’ al-Din, Imam Sadiq, peace be upon him, said: 'The Takbir on Eid al-Fitr and Eid al-Adha is obligatory. On Eid al-Fitr, it is during five prayers, starting from the Maghrib prayer on the night of Eid al-Fitr until the Asr prayer on the day of Eid al-Fitr, and it is said as follows:'

اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ لَا إِلَهَ إِلَّا اللَّهُ وَ اللَّهُ أَكْبَرُ وَ لِلَّهِ الْحَمْدُ اللَّهُ أَكْبَرُ عَلَى مَا هَدَانَا وَ الْحَمْدُ لِلَّهِ عَلَى مَا أَبْلَانَا

This is due to the saying of Allah, the Almighty, in Surah Al-Baqarah, verse 185: 'So that you complete the number and say Takbir to Allah for what He has guided you!'

لِتُكْمِلُوا الْعِدَّةَ وَ لِتُكَبِّرُوا اللَّهَ عَلى ما هَداكُمْ

✅ Based on the above narrations, when the crescent of Shawwal is confirmed, after five prayers, i.e., after the Maghrib and Isha prayers on the night of Eid al-Fitr, after Fajr prayer, after Zuhr, and after Asr prayer on the day of Eid al-Fitr, or after four prayers: after Maghrib, after Isha on the night of Eid al-Fitr, after Fajr on the day of Eid al-Fitr, and after Eid prayer, we say:

Or we say:

اللَّهُ أَکْبَرُ اللَّهُ أَکْبَرُ لَا إِلَهَ إِلَّا اللَّهُ وَ اللَّهُ أَکْبَرُ اللَّهُ أَکْبَرُ وَ لِلَّهِ الْحَمْدُ اللَّهُ أَکْبَرُ عَلَی مَا هَدَانَا

✅ Of course, to follow both narrations, one can say these Takbirs after Maghrib, Isha, Fajr, Eid prayer, Zuhr, and Asr prayers.

✅ The Takbirs of Eid al-Adha have differences, which will be presented in separate narrations.

اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ لَا إِلَهَ إِلَّا اللَّهُ وَ اللَّهُ أَكْبَرُ وَ لِلَّهِ الْحَمْدُ اللَّهُ أَكْبَرُ عَلَى مَا هَدَانَا وَ الْحَمْدُ لِلَّهِ عَلَى مَا أَبْلَانَا

اللَّهُمَّ صَلِّ عَلَی مُحَمَّدٍ و آلِ مُحَمَّدٍ و عَجِّلْ لِوَلِیِّکَ الْفَرَج