As discussed under Alma 46:7, there was a tendency for Oliver Cowdery to write the plural hands in the phrases “by the hand of the Lord” and “by the hand of God”. Except for the one case of “by the hands of the Lord” in Alma 46:7, the earliest text consistently supports the singular hand in these two phrases, including here in Alma 46:24. In this instance, Oliver initially wrote the plural hands in 𝓞 but then immediately erased the plural s. Elsewhere in the text, there are three examples of “by the hand of God” but none of “by the hands of God”:
For a list of cases where hand and hands have been mixed up in the text, see under Mosiah 16:1.
Summary: Maintain in Alma 46:24 the singular hand, the immediately corrected reading in 𝓞 (“by the hand of God”).