Musnad Ahmad 1153:656

Muhammad ibn Ubayd narrated to us, Ubayd Allah narrated to us, from Abd al-Rahman ibn al-Qasim, from his father, from Aisha, that she said: "I wished that I had sought permission from the Messenger of Allah, peace and blessings of Allah be upon him, just as Sawda sought his permission, so that I could pray the morning prayer in Mina and arrive before the people came." They said to Aisha: "And did Sawda seek his permission?" She said: "She was a heavy, slow woman, so he gave her permission."