We have an interesting scene presented here. Noah feels something in the words of Abinadi. He has seen the power of the spirit in Abinadi, and now must have felt something in these words of clear condemnation. Noah does not want to be condemned, and so rather than have Abinadi recant, Noah is on the verge of recanting his own decree.
It is the priests who do not allow it. More than Noah, the priests have born the brunt of Abinadi's accusations. It was they who were accused of teaching falsely, and therefore it was they who had the greatest hatred for Abinadi. The way they push Noah to action is interesting. They remind the king that Abinadi has spoken against the king. With the common presumption of the divine nature of kings throughout most of the world, this was again tantamount to blasphemy, but in this case a personal blasphemy against the person of the king. The priests used Noah's vanity in believing too much of himself against him. They appealed to his pride, and therefore firmed the death penalty against Abinadi.