Musannaf Ibn Abi Shayba 9:1693

Zayd ibn al-Hubab narrated to us, from al-Dahhak ibn Uthman, who said: Zayd ibn Aslam informed me, from Abd al-Rahman ibn Abi Sa'id al-Khudri, from his father, that the Messenger of Allah (may Allah bless him and grant him peace) said: "A woman shall not touch a woman while in a single garment, and a man shall not touch a man while in a single garment."