Musannaf Ibn Abi Shayba 3:3792

Isa ibn Yunus narrated to us, from al-Awza'i, from Makhul, who said: I asked Aisha, "In how many [garments] should a woman pray?" She said, "Go to Ali and ask him, then return to me." So he went to Ali and asked him. He said, "In a full-length chemise (dir') and a head covering (khimar)." He returned to her and informed her, and she said, "He spoke the truth."