This is one of the greatest Sunnahs on the day of Eid.
The time for takbeer on Eid al-Fitr starts from the night before Eid until the imam enters to lead the Eid prayer.
Description of the takbeer:
It was narrated in the Musannaf of Ibn Abi Shaybah with a saheeh isnaad from Ibn Mas’ood (may Allaah be pleased with him) that he used to recite takbeer during the days of tashreeq:
Allaahu akbar, Allaahu akbar, laa ilaaha ill-Allaah, wa Allaahu akbar, Allaah akbar, wa Lillaah il-hamd (Allaah is Most Great, Allaah is most Great, there is no god but Allaah, Allaah is Most great, Allaah is most great, and to Allaah be praise). #Sunnah #Eid