Sahih Bukhari Volume 8, Book 76, Hadith Number 431.

Narated By ‘Utban bin Malik Al-Ansari : Who was one of the men of the tribe of Bani Salim: Allah’s Apostle came to me and said, “If anybody comes on the Day of Resurrection who has said: La ilaha illal-lah, sincerely, with the intention to win Allah’s Pleasure, Allah will make the Hell-Fire forbidden for him.”