Is it true that there are four days of celebration of Eid Adha? Does that imply we can't fast for 4 days whether we sacrifice an animal or not?
Narrated Uqbah ibn Amir: The Prophet (ﷺ) said: The day of Arafah, the day of sacrifice, the days of tashriq are (the days of) our festival, O people of Islam. These are the days of eating and drinking. [Sunan abi Dawod and other Versions in other Sunan Books]
Nubaisha al-Hudhali reported Allah's Messenger (ﷺ) as saying: The days of Tashriq are the days of eating and drinking. [Sahih Muslim]
It was narrated from Abu Hurairah that the Messenger of Allah (ﷺ) said: “The days of Mina (11th, 12th, and 13th of Dhul-Hijjah) are days of eating and drinking.’” [Sunan ibn Majah]
Related Question but didn't get my answer: What days are you meant to fast in dhul hijjah