Asking a sister's permission to enter

Ata' said, "I asked Ibn 'Abbas, 'Does one ask permission of one's sister?' He replied, 'Yes.' I repeated it and said, 'My two sisters live in my room and I provide for them and spend on them, so do I ask them for permission?' He said, 'Yes. Do you want to see them naked?' Then he recited, 'O you who believe! Those you own as slaves and those of you who have not as yet reached puberty should ask your permission to enter at three times: before the Dawn Prayer and when you have undressed at noon and after the Night Prayer - three times of nakedness for you.' (24:56) Ibn 'Abbas said, 'He did not command these individuals to ask permission other than at these three times of nakedness.' Then he went on to say, 'The verse in Surat an-Nur:57 is: 'Once your children have reached puberty, they should ask your permission to enter as those before them also asked permission.'"