It is permissible for a wife to give her turn to a co-wife Sahih Muslim 1465 a
Translation
'Ata related that when they were with Ibn 'Abbas (Allah be pleased with them) at the funeral of Maimuna In Sarif, Ibn 'Abbas (Allah be pleased with them) said
This is the wife of Allah's Apostle (ﷺ) ; so when you lift her bier, do not shake her or disturb her, but be gentle, for Allah's Messenger (ﷺ) had nine wives, with eight of whom he shared his time, but to one of them, he did not allot a share. 'Ati said: The one to whom he did not allot a share of time was Safiyya, daughter of Huyayy b. Akhtab.