Abram is the first mentioned prophet in the book of Genesis, but was there another before him? In the book of Jude, we are told that Enoch, a man who lived in the pre-flood era was a prophet, but was he the first? No, we are told of another, the first prophet, Abel. How do we know he was a prophet? Jesus calls him out to be one. In talking with the Scribes and Pharisees, he said:
“Woe to you! For you build the tombs of the prophets, and it was your fathers who killed them. So you are witnesses and approve the deeds of your fathers; because it was they who killed them, and you build their tombs.For this reason also the wisdom of God said, ‘I will send to them prophets and apostles, and some of them they will kill and some they will persecute, so that the blood of all the prophets, shed since the foundation of the world, may be charged against this generation, from the blood of Abel to the blood of Zechariah*, who was killed between the altar and the house of God; yes, I tell you, it shall be charged against this generation.’” (Luke 11:49-51)
Very little is known about Abel, but we know he was a righteous man who offered a sacrifice before the Lord. He was also a shepherd, “a keeper of flocks” who was killed by his older brother Cain in a jealous rage. Being a prophet, Abel was selected by God to speak for him. This would have thrown fuel onto the fire which burned in Cain. We have no record of what Abel prophesied to his parents, brothers and sisters, but he was a prophet none-the-less – one who spoke for God.
*Note: Abel is the first of the prophets Jesus mentions and Zechariah is the last. Zechariah is mentioned in 2 Chronicles, which may appear to be troublesome since Zechariah is not the last prophet mentioned in the Old Testament. However, it is our current arrangement of the Hebrew Bible that is different from the one Jesus knew and referenced. The Hebrew Bible, or Tanakh, is the Bible that Jesus and his listeners were familiar with. And in this arrangement, 2 Chronicles is the last book, meaning that Zechariah is in the correct order as being the last of the martyred prophets.