The 1874 RLDS edition accidentally changed the plural messengers to the singular messenger; this incorrect reading has persisted in the RLDS text. The surrounding sentences, listed as 1 and 3 below, clearly show that the plural listed under 2 is correct:
Summary: Maintain in Alma 43:24 the plural messengers, the reading in the earliest textual sources (including 𝓞); the nearby text consistently refers to the messengers in the plural.