They entered upon Hafsah bint 'Abdur-Rahman to ask her about the 'Aqiqah. She informed them that 'Aishah had informed her, that the Messenger of Allah (ﷺ) ordered them that for a boy, two sheep were sufficient, and for a girl one sheep.
Jami` at-Tirmidhi Book 19, Hadith 24
← Previous Hadith 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.

Jami` at-Tirmidhi Book 19, Hadith 23 Next Hadith → That his father said: "I saw the Messenger of Allah (ﷺ) say the Adhan in the ear of Al-Hasan bin 'Ali - when he was born to Fatimah - the Adhan of Salat."

Jami` at-Tirmidhi Book 19, Hadith 25