فَمَا يَكُنْ فِي كِتَابِي هَذَا مِنْ خَبَرٍ مُسْتَنْكَرٍ … فَلْيَعْلَمْ أَنَّهُ لَمْ يُؤْتَ فِي ذَلِكَ مِنْ قِبَلِنَا، وَإِنَّمَا أُتِيَ مِنْ قِبَلِ بَعْضِ نَاقِلِيهِ إِلَيْنَا، وَأَنَا إِنَّمَا أَدَّيْنَا ذَلِكَ عَلَى نَحْوِ مَا أُدِّيَ إِلَيْنَا.
Whatever in this book of mine is a report that is found objectionable — let the reader know it did not come from us. It came from some who transmitted it to us. We have only delivered it as it was delivered to us.
al-Tabari, introduction to the Tarikh
This is the key of the whole work. He is a trustee of transmission, not a guarantor of every story.