Sahih Muslim Book 41, Hadith Number 6887.
Chapter : The sinking of an army in the earth which would attack the House.
This hadith has been narrated on the authority of ‘Abdullah b. Rufai, with the same chain of transmitters (but with the addition of these words): “When I met Abu Ja’far I told him that she (simply) meant the plain ground. Thereupon Abu Ja’far said: No, by God, she meant the plain ground of Medina.