The angel’s appearance was in answer to the prayers of King Benjamin because of his righteousness (v. 4). The Nephites “believed in Christ and worshipped [and thus prayed to] the Father in his name” (Jacob 4:5; see also 3 Nephi 18:19). It was the Lord Omnipotent who sent the angel to answer the prayer. The Lord Omnipotent, who is Christ (Mosiah 3:17), was to come to the earth (v. 5). Jesus said “the Father and I are one (3 Nephi 28:10), and thus may speak for each other.
“Glad tidings of great joy” (Mosiah 3:3) is the English translation of the Hebrew word for gospel. The declaration the angel was about to give would cause King Benjamin and his people to rejoice, and be filled with joy (v. 4). The angel’s knowing that his message would bring the people joy is an indicator of their present righteousness. As we review that message, we can appreciate why the angel said they would rejoice and be filled with joy.