Musnad Ahmad 32:1294

'Affan narrated to us, Hammad ibn Salamah narrated to us, he said: Humayd informed us, from Musa ibn Anas ibn Malik, from Anas, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "You have left behind in Medina men; you have not traveled any distance, nor spent any expenditure, nor crossed any valley, but they were with you in it." They said: "O Messenger of Allah, how can they be with us while they are in Medina?" He said: "The excuse detained them."