Sunan an-Nasa'i, Volume 3, Book 21, Hadith 1889 (DarusSalam) ⓘ
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)."
أَخْبَرَنَا 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 " .
also referenced under: Hadith 1888 (Reference) & Book 21, Hadith 71 (In-Book)