Musnad Ahmad 27:314

Waki’ narrated to us, Al-‘Umari narrated to us, from Nafi’, from Ibn ‘Umar, and from ‘Abd al-Rahman ibn al-Qasim, from his father, from ‘Aisha: "That the Prophet, may Allah bless him and grant him peace, had a *lahd* (a niche in the side of the grave) made for him."