Musnad Abu Ya'la al-Mawsili 152:201

Al-Hasan ibn ‘Umar ibn Shaqiq narrated to us, Ma‘ruf ibn Hassan narrated to us, from Sa‘id, from Qatadah, from Ibn Buraydah, from ‘Abdullah ibn Mas‘ud, that he said: The Messenger of Allah (ﷺ) said: "If the mount of one of you escapes in a desolate land, then let him call out: 'O servants of Allah, restrain [it]! O servants of Allah, restrain [it]!' For indeed, Allah has those present on the earth who will restrain it for him."