What is the reason for the revelation of the verse: (And those of your women who have despaired of menstruation)?

The verse "And those who have despaired of menstruation" is not in Surat Al-Baqarah, but rather in Surat At-Talaq (the minor Surat An-Nisa). The verse was revealed after Ubayy ibn Ka'b asked the Prophet, peace and blessings be upon him, about the waiting period (iddah) for young girls, elderly women, and pregnant women. Then it was revealed: "And those of your women who have despaired of menstruation – if you doubt, then their waiting period is three months – and those who have not menstruated. And for those who are pregnant, their term is until they deliver their burdens."