Sayyiduna Salamah bin al-Akwa' (may Allah be pleased with him) narrates: I was with the Prophet (peace and blessings be upon him) when a man came and entered the mosque. He (peace and blessings be upon him) said: "Catch him, for he is a spy." So I caught up with him, and since I was swift, I killed him, and the Prophet (peace and blessings be upon him) gave me his belongings.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6246