اَللَّهُ أَكْبَرُ اَللَّهُ أَكْبَرُ، لَا إِلَهَ إِلَّا اللَّهُ، وَاللَّهُ أَكْبَرُ اَللَّهُ أَكْبَرُ، وَلِلَّهِ الْحَمْدُ
Transliteration
Allahu akbar Allahu akbar, la ilaha illallah, wallahu akbar Allahu akbar, wa lillahil-hamd
English meaning
Allah is the Greatest, Allah is the Greatest. There is no deity except Allah. Allah is the Greatest, Allah is the Greatest. To Allah belongs all praise.
When is it recited?
Mornings of Eid al-Fitr and Eid al-Adha.
Source
Bayhaqi III/315