Al-Husayn ibn Sa‘id, from Fadalah, from Al-‘Ala’, from Muhammad ibn Muslim, from one of the two (Imams عليه السلام), peace be upon them:
Imam عليه السلام said: "Do not perform the obligatory prayer inside the Ka‘bah."
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 2, p. 405