During Abinadi's first mission the Lord had him call the people to repentance. This mission is different. Abinadi does not deliver a prophetic if but rather a prophetic will. Abinadi now foretells their bondage and suffering. The people have made their decision, and the Lord has made his. Abinadi simply describes the imminent future of the unrepentant population. These fearsome calamities will all too soon become the reality of their lives.
Textual: Mormon appears to be citing a record of Abinadi's speech. However, it is also clear from internal evidence that there was no single account of the speech (see verses 10-12 below). It would have been very surprising to have a single account of this part of Abinadi's discourse because it was made to a public that was not expecting him. There would have been no way that someone would have happened to have the writing materials with him to record the precise words.
Mormon's source here is the official record of Noah, and the source of that record had to be the oral remembrances of those in the crowd. Those remembrances were not complete, and lead to slightly differing versions of what he said (again see 10-12 below).