Musannaf Ibn Abi Shayba 28:744

Waki’ narrated to us, he said: Jarir ibn Hazim narrated to us, from al-Hasan, he said: Ibn ‘Amir sent a captive to Ibn ‘Umar while he [Ibn ‘Umar] was in Fars or in Istakhr, for him to kill him. Ibn ‘Umar said: "As for while he is *masrur*, then no." Waki’ said: Meaning, tied up.