Fairly soon afterwards, King Lamoni wanted to take Ammon to meet Lamoni’s father, the king of all the land of Nephi. But Ammon received a revelation telling him that his brother Aaron and two other missionaries were imprisoned and that he needed to go and free them. Ammon told king Lamoni about the situation, who responded with faith, “I know, in the strength of the Lord thou canst do all things” (20:4). Lamoni was curious as to how Ammon knew about the perilous situation of his brother, so Ammon told him, “No one hath told me, save it be God; and he said unto me—Go and deliver thy brethren, for they are in prison in the land of Middoni” (20:5). Lamoni decided to join Ammon on his journey to Middoni, promising to use his influence as king to persuade the king of Middoni, who was a friend of his, to release the missionaries from prison. On the way to Middoni, Ammon and Lamoni met up with Lamoni’s father who was “king over all the land” (20:8).
Book of Mormon Central, “What Did It Mean to Be ‘King Over All the Land? (Alma 20:8),” KnoWhy 128 (June 23, 2016).