Is it valid to perform I'tikaf in any mosque?

Scholars have differed regarding the description of the mosque in which I'tikaf (spiritual retreat) is valid. Some have held that I'tikaf is valid in any mosque, while Imam Ahmad stipulated that the mosque must be one where congregational prayers are established. He based this on the saying of 'Aisha and Ibn Abbas (may Allah be pleased with them): "There is no I'tikaf except in a congregational mosque," and because performing I'tikaf in a mosque where congregational prayers are not established leads to abandoning the congregation or frequent exiting, which contradicts the purpose of I'tikaf. This condition applies specifically to men. As for women, their I'tikaf is valid in any mosque, because congregational prayer is not obligatory for them.