Uqba bin 'Amir al-Juhayni · The Book on Sacrifices

"The Messenger of Allah (ﷺ) ordered that we check the eyes and ears, and not to slaughter the Muqabalah, nor the Mudabarah, nor the Sharqa', nor the Kharqa'"

That the Messenger of Allah (ﷺ) said: "There is no Fara' or 'Atirah." The Fara' is the first of the offspring that would be born to them, so they would slaughter it. The 'Atirah was an animal that they would slaughter during Rajab to honor the month of Rajab, since it was the first of the sacred months.