After quoting king Benjamin, Helaman invokes Amulek’s sermon to Zeezrom in Ammonihah. While the coming Messiah would redeem humankind from sin, the redemption is from sin upon conditions of repentance, for humanity cannot be saved while in unrepentant sin.
Helaman had been the record keeper, as his father had been. He not only kept the record, he had clearly read it and learned from it. Although the Nephites only used the word scripture to refer to the plates of brass, Helaman, nevertheless, considered the more religious parts of the record as scripture. In the case of Amulek and Zeezrom, Helaman had also read the separate account that Alma, his grandfather, had kept. Perhaps the fact that it was written by his grandfather made it even more important that he read and understand it.