Sahih Bukhari
To make the Heart Tender (Ar-Riqaq)
Volume: 008 / Book Number: 076 / Hadith Number: 431
Narrated '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."