Nahj al-Balagha itself does not have any Isnad (chains of narrators), but it is possible to find the Isnad of much of its contents in other sources. It is not possible to rule an overall judgment about the whole book, in terms of reliability. Rather every sermon, letter or saying should be looked at from other sources separately.

An interesting point about Nahj al-Balagha is that while there are a number of places in this book where it is narrated that Ali (ra) was arguing about his right to Khilafa, in no place in this book is there any reference to him being selected by God to be Khalifa or Imam after the prophet (sws) and there is no reference to him being announced as the prophet’s successor. In fact, in all places where these arguments (in favor of Ali having right to Khilafa) are narrated, they are based on kinship and knowledge rather than being appointed.

The Khutba of Sheqsheqya is one example, where you see that despite apparently very open criticism of other companions, there is no mention of Ali (ra) being appointed by the prophet as his successor. This sermon has a few chains of narrators and none of them are flawless, even according to the books of Rijal of Shia.