The Pulpit Commentary on Luke 6:12

And it came to pass in those days. That is to say, in the course of his ministry in Galilee, especially in the thickly populated district lying round the Lake of Genessaret, and after the events related in Luke 5:1-39. and the first eleven verses of Luke 6:1-49., Jesus proceeded to choose, out of the company of those who had especially attached themselves to him, twelve who should henceforth be always with him. These he purposed to train up as the authorized exponents of his doctrine, and as the future leaders of his Church. Things had assumed a new aspect during the last few months. Jerusalem and the hierarchy, supported by the great teachers of that form of Judaism which for so long a period had swayed the hearts of the people, had, although not yet openly, declared against the views and teaching of Jesus. His acts?봟ut far more his words?봦ad gathered round him, especially in Galilee, in the north and central districts of Palestine, a large and rapidly increasing following. It was necessary that some steps should be taken at once to introduce among the people who had received his words gladly, some kind of organization; hence the formal choice of the twelve, who from henceforth stood nearest to him. We possess the following four lists of these twelve men:??

Matthew 10:2-4

Mark 3:16-19