Musnad Abu Ya'la al-Mawsili 153:108

Al-Husayn ibn al-Aswad narrated to us, Abu Usamah narrated to us, Umar ibn Hamzah narrated to us, Salim informed me, Abdullah ibn Umar informed me that the Messenger of Allah (may Allah bless him and grant him peace) was brought Hatib ibn Abi Balta'ah. The Messenger of Allah (may Allah bless him and grant him peace) said to him, "You wrote this letter?" He said, "Yes. But by Allah, O Messenger of Allah, it was not because of a lack of faith in my heart, but there was no one from Quraysh except that he had family and servants who would protect his family for him, so I wrote a letter hoping that Allah would protect my family for me through it." Umar said, "Permit me [to strike] him." The Messenger of Allah (may Allah bless him and grant him peace) said, "Would you have killed him?" He said, "Yes, if you had permitted me." The Messenger of Allah (may Allah bless him and grant him peace) said, "And what do you know? Perhaps Allah looked upon the people of Badr and said, 'Do what you wish.'"