Muhammad bin Ishaq narrated that I asked Abu Ja'far Muhammad bin Ali, "What was in the scroll that was in the sheath of the Messenger of Allah’s ﷺ sword?" He replied: "It contained that Allah has cursed the one who kills someone other than his killer, and has also cursed the one who strikes someone other than his striker. And whoever gives someone’s blessing to a non-guardian as an owner, he has denied the revelation that Allah Almighty sent down upon Muhammad ﷺ."
Hadith Referenceمسند الإمام الشافعي / كتاب القتل والقصاص والديات والقسامة / 1619
Hadith Takhrijاسناده ضعيف لإعضاله اخرجه البيهقي: 26/8 - وفى المعرفة السنن والآثار له (4798)۔