God calls those who are available for the job at hand.
But prophesy not again any more at Bethel: for it is the king’s chapel, and it is the king’s court. Then answered Amos, and said to Amaziah, I was no prophet, neither was I a prophet’s son; but I was an herdman, and a gatherer of sycomore fruit: And the LORD took me as I followed the flock, and the LORD said unto me, Go, prophesy unto my people Israel. (Amos 7:13-15 KJV)
Amos was a common or ordinary man, nobody special, and was never formally educated in any truths of God. However, he stood his ground towards Amaziah who tried to run him off from prophesying in the chapel. He made the case that Amos did not belong in Bethel, especially prophesying in front of a group of men in the front of the king’s chapel.
Amaziah understood that he did belong in the chapel. He had been formally called by God into service; even as a lowly shepherd boy tending to his flock. He was hand-picked from the hand of God. God called men who were available and of humble means for prophesying of what was to come. He selected the best of the best for this purpose; men like Isaiah, Jeremiah, Daniel, and Ezekiel, along with many others who served God’s purposes heartily in their appointed time of godly service.
God still calls those who are available but He is no longer in need of prophets as His Word is complete. He now calls mankind to sow seeds of His gospel message to others who need to hear His message of hope amid spiritual desolation in this world.