It is narrated from Hazrat Samurah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: No man should take his brother as a captive and then kill him.
Hadith Referenceمسند احمد / أول مسند البصريين / 20201
Hadith Gradingحکم دارالسلام:إسناده ضعيف لضعف بقية بن الوليد وإسحاق بن ثعلبة، ومكحول لم يسمع من سمرة