Musannaf Ibn Abi Shayba 28:967

Waki’ narrated to us, he said: Sufyan narrated to us, from Shu’bah, from ‘Amr ibn Dinar, from ‘Ikrimah, regarding the saying of Allah: "And prepare against them whatever you are able of power," he said: "The fortresses." He said regarding: "And of steeds of war," he said: "The females."