Sayyiduna Jabir (may Allah be pleased with him) narrated: A man came to the Prophet (peace and blessings be upon him) and said: "My neighbour is a hypocrite; he does such-and-such things." The Prophet (peace and blessings be upon him) asked: "Does he say La ilaha illallah (there is no god but Allah)?" The man replied: "Yes!" The Prophet (peace and blessings be upon him) said: "I have been forbidden (from killing) such people (that is, those who profess the testimony of faith)."
Imam al-Bazzar recorded it. Its chain contains mastur (unknown-status) narrators, and the narrator Muhammad bin Abi Layla had a poor memory.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الإيمان / 44