أَخْبَرَنَا هَارُونُ بْنُ عَبْدِ اللَّهِ، قَالَ حَدَّثَنَا مَعْنٌ، قَالَ حَدَّثَنَا مَالِكٌ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ كَانَ الرِّجَالُ وَالنِّسَاءُ يَتَوَضَّئُونَ فِي زَمَانِ رَسُولِ اللَّهِ صلى الله عليه وسلم جَمِيعًا ‏.‏

It was narrated that Ibn 'Umar said: "Men and women used to perform Wudu' together during the time of the Messenger of Allah (PBUH)." Translation Not Available

Book reference: Sunan An Nisai Book 2 Hadith 342
Web reference: Sunan An Nisai Volume 1 Book 2 Hadith 343