Hadith 29:112
Ibn ‘Uyaynah narrated to us, from Muhammad ibn ‘Abd al-Rahman, from his father, who said: When ‘Umar arrived at the conquest of Tustar—and Tustar is from the land of Basra—he asked them, "Is there any stranger?" They said, "A man from the Muslims joined the polytheists, so we captured him." He said, "What did you do with him?" They said, "We killed him." He said, "Would that you had put him in a house, locked a door upon him, and fed him a loaf of bread every day until you had sought his repentance for three days. If he repented, [it would be well], and if not, you would have killed him." Then he said, "O Allah, I did not witness it, I did not command it, and I was not pleased when it reached me," or "when it reached me."
حدثنا بن عيينة عن محمد بن عبد الرحمن عن أبيه قال لما قدم عمر فتح تستر وتستر من أرض البصرة سألهم هل من مغربة قالوا رجل من المسلمين لحق بالمشركين فأخذناه قال ما صنعتم به قالوا قتلناه قال أفلا أدخلتموه بيتا وأغلقتم عليه بابا وأطعمتموه كل يوم رغيفا حتى استتبتموه ثلاثا فإن تاب وإلا قتلتموه ثم قال اللهم لم أشهد ولم آمر ولم أرض إذ بلغني أو حين بلغني