The readings from Amos and Mark tell about people who receive a mission. In both cases the people with the mission are rather ordinary: Amos is a shepherd and tree dresser, the apostles are mostly fishermen.
The latter symbolize the ordinary people through whom God works for the salvation of the world.
Many people stay out of the struggle for a better world, believing that only important people and the specially talented make a difference. They should remember this shepherd and these fishermen.
These messengers carry similar messages. The apostles preached the need for repentance, that is, the need for people to change their way of living.
Amos also spoke about the need to live differently, and that is why the priest was throwing him out of Bethel. The established religion of the Northern Kingdom, centered in Bethel, felt threatened by this prophet of social justice.
In the religion of Amos, “God proclaims peace to his people and justice shall look down from heaven so that justice and peace shall kiss.” Amaziah wanted nothing of that.
The apostles were to take nothing with them on the journey but their companionship (“two by two”) and the authority they received from Jesus. Their mission was to confront the evil embodied in society and to “reject what is contrary to the Gospel.”
The laity share in the priestly, prophetic, and royal office of Christ and therefore have their own role to play in the mission of the whole People of God in the Church and in the world. They exercise a genuine apostolate by their activity on behalf of bringing the gospel and holiness to men, and on behalf of penetrating and perfecting the temporal sphere of things through the spirit of the Gospel.
Vatican II, Decree on the Apostolate of the Laity,
1965: paragraph 2.