Al-Suyuti in Tafsir Durr Al-Mansoor, Vol13, Pg322 says:
Narrated Ibn Al-Monzir from Awn Ibn Abi Shaddad who said: Umar had a slave-girl who embraced Islam
before him. She was called Zennaira. Because of her conversion to Islam Umar used to hit her, and the
disbelievers of Quraysh used to say: If Islam was a good thing, Zennaira would not have preceded us in it, whereupon
Allah (swt) revealed a verse in the Qur’aan: {And those who disbelieve say of those who believe: 'Had it (Islam) been a
good thing, they (the weak and poor) would not have preceded us thereto!'}[46:11]
Alkarbala