Narrated 'Abdullah bin 'Amr bin Al-'As:
that the Messenger of Allah (sulla allahu aleihi wa sallam) said:
"Indeed Allah will distinguish a man from my Ummah before all of creation on the Day of Judgement. Ninety-nine scrolls will be laid out for him, each scroll is as far as the eye can see, then He will say: 'Do you deny any of this? Have those who recorded this wronged you?'
he will say: 'No, O Lord!'
HE will say: Do you have an excuse?'
he will say: 'No, O Lord!'
So HE will say: 'Rather you have a good deed with us, so you shall not be wronged today." Then HE will bring out a card (Bitaqah); on it will be: "I testify to La Ilaha Illallah, and I testify that Muhammad is His servant and Messenger."
HE will say: 'Bring your scales.' he will say: 'O Lord! What good is this card next to these scrolls?'
HE will say: 'You shall not be wronged.'
He said: 'The scrolls will be put on a pan (of the scale), and the card on (the other) pan: the scrolls will be light, and the card will be heavy, nothing is heavier than the Name of Allah.'"
Reference : Jami` at-Tirmidhi 2639
In-book reference : Book 40, Hadith 34
English translation : Vol. 5, Book 38, Hadith 2639
Source:
http://sunnah.com/tirmidhi/40/34