Jonas was one of the twelve disciples Jesus chose during his ministry to the Nephites, and the son of Nephi, who was also among the twelve (3 Nephi 19:4). The list in which he is named includes a second man also called Jonas; Jonas the son of Nephi is the one distinguished by his father.
Jesus gave the twelve power and authority to baptize and called them to minister to the people as their servants (3 Nephi 12:1). When Jesus later asked the disciples what they desired of him after he had gone to the Father, nine of the twelve asked that their ministry end at the age of man so they could come to him in his kingdom, and he promised them they would come to him at seventy-two years old (3 Nephi 28:3).