Musnad Abu Ya'la al-Mawsili 115:152

Musa ibn Abd al-Rahman narrated to us, Umar ibn Sa'id al-Abbah narrated to us, from Sa'id, from Qatadah, from Anas, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "He who says 'There is no god but Allah' and has in his heart the weight of a barleycorn of goodness will be brought out of the Fire. And he who says 'There is no god but Allah' and has in his heart the weight of a grain of wheat of goodness will be brought out of the Fire. And he who says 'There is no god but Allah' and has in his heart the weight of an atom of goodness will be brought out of the Fire." It was said to Sa'id, "O Abu al-Nadr, will they be brought out after they have been entered [into it]?" He said, "Are you not Arabs? There can be no 'bringing out' except after an 'entering'."