Oliver Cowdery here initially wrote “the will of God”. He immediately caught his error, crossed out God, supralinearly wrote the, and then continued inline by writing Lord. Thus there is no doubt that 𝓞 read “the will of the Lord”. Theoretically, either reading is possible; elsewhere in the text, there are seven occurrences of “the will of God” and three more of “the will of the Lord”. Thus there would have been no motivation for Oliver to have emended the text here.
Summary: Maintain in Alma 14:13 the immediately corrected reading in 𝓟, “the will of the Lord”.