(1) باب وَقْتِهَا
Anas b. Malik reported:
Allah's Messenger (ﷺ) addressed us on the day of 'Id al-Adha. He smelt the odour of flesh and he prohibited thern from slaughtering (the animals before the 'Id prayer), saying: He who slaughtered the animals (before the 'Id prayer) should do that again (as it is not valid as a sacrifice).
Reference: Sahih Muslim 1962 c
In-book reference: Book 35, Hadith 18
USC-MSA web (English) reference(deprecated numbering scheme): Book 22, Hadith 4835