Hadith 11:257
Ibn al-Mubarak narrated to us, he said: I said to ‘Ata’, "Is the military expedition (ghazw) obligatory?" He said, "He and ‘Amr ibn Dinar said: 'We do not know.'"
حدثنا بن المبارك قال قلت لعطاء الغزو واجب فقال هو وعمرو بن دينار ما علمنا