Narrated Abu Bakra: Allah's Apostle said thrice, Shall I not inform you of the biggest of the great sins? We said, Yes, O Allah's Apostle He said, To join partners in worship with Allah: to be undutiful to one's parents. The Prophet sat up after he had been reclining and added, And I warn you against giving forged statement and a false witness; I warn you against giving a forged statement and a false witness. The Prophet kept on saying that warning till we thought that he would not stop.