Sunan an-Nasa'i 1888
سنن النسائي#1888Sahihأَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا حَمَّادٌ، عَنْ أَيُّوبَ، عَنْ حَفْصَةَ، عَنْ أُمِّ عَطِيَّةَ، نَحْوَهُ غَيْرَ أَنَّهُ قَالَ " ثَلاَثًا أَوْ خَمْسًا أَوْ سَبْعًا أَوْ أَكْثَرَ مِنْ ذَلِكِ إِنْ رَأَيْتُنَّ ذَلِكِ " .
Something similar was narrated from Umm 'Atiyyah except, that he (the narrator) said:"Three times or five, or seven, or more than that, if you think that (is necessary)
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih - Agreed Upon
In-book reference: 21:71