Moroni had declared in verse 20 of this chapter that “the reason why [God] ceaseth to do miracles among the children of men is because that they dwindle in unbelief.” What happens when that condition is reversed, and the children of men repent and believe? Miracles return. God is constant, and when we are worthy of the miracles through our faith in Jesus Christ, the miracles can return. Thus, those miracles can become a sign of the righteous.
The language of verse 24 follows Mark 16:17–18: “And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues; They shall take up serpents; and if they drink any deadly thing, it shall not hurt them; they shall lay hands on the sick, and they shall recover.”