Sahih Bukhari
Oneness, Uniqueness of Allah (Tawheed)
Volume: 009 / Book Number: 093 / Hadith Number: 600
Narrated Anas:
I heard the Prophet saying, "On the Day of Resurrection I will intercede and say, "O my Lord! Admit into Paradise (even) those who have faith equal to a mustard seed in their hearts." Such people will enter Paradise, and then I will say, 'O (Allah) admit into Paradise (even) those who have the least amount of faith in their hearts." Anas then said: As if I were just now looking at the fingers of Allah's Apostle.