As in the previous verse, Oliver Cowdery initially wrote the Lord instead of God as he copied from 𝓞 into 𝓟. His correction is just like the one in verse 4 (supralinear and without any change in the level of ink flow). Here the phraseology involves “the hand of X”. In the text there are examples of both “the hand of the Lord” and “the hand of God”, with the first clearly dominating (25 to 5). In each case, we let the earliest textual sources determine which of the two readings is correct.
Summary: Maintain in Mosiah 1:5 the corrected reading in 𝓟: “by the hand of God”.