Sayyiduna Iyad al-Ansari (may Allah be pleased with him) narrates it as a marfu' hadith: The Prophet (peace and blessings be upon him) said: "La ilaha illallah is an honoured word in the sight of Allah Almighty, and it holds a lofty station with Allah Almighty. It is a word such that whoever says it sincerely, Allah Almighty will admit him into Paradise because of it. And whoever says it falsely, this word will protect his life and safeguard his wealth, and tomorrow, when he presents himself before Allah Almighty, Allah Almighty will take him to account."
Al-Bazzar recorded it, and its narrators have been declared trustworthy, if its Tabi'i is Abd al-Rahman bin Abdullah bin Mas'ud.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الإيمان / 55