Musannaf Ibn Abi Shayba 9:1388

Abu Bakr narrated to us, he said: Ibn ‘Uyaynah narrated to us, from ‘Amr, from Muhammad ibn ‘Ali, who said: Al-Hasan and Al-Husayn did not consider [it permissible to] see the Mothers of the Believers. And Ibn ‘Abbas held the view that seeing them was permissible for them.