Amillennialism owes its major impetus to the well-known Catholic theologian Augustine.
He decided that the kingdom could not be literal, holding that there will be no physical, earthly millennial kingdom over which Christ will rule. To Augustine, it must be a spiritual kingdom. The kingdom of God, he declared, was “in the hearts” of faithful men, not in an actual literal kingdom on the earth over which Christ would one day rule.
At first, he was convinced that the thousand-year kingdom of which the Bible spoke would be the period of time between the first and second advents of Christ. In time, however, he became disillusioned because the description of the kingdom in the Bible did not fit the reality of the world in which he lived. Subsequently he developed a form of interpretation that regards all of the Bible as subject to literal interpretation, but allegorizes prophetic Scripture. Under this system of interpretation, the Bible became a subjective patchwork which could be made to say whatever one wanted it to say.
In Luke 4:16-21, Jesus declared that He was the fulfillment of the prophecy in Isa. 61:1-2. The Messiah will bind up the brokenhearted, release prisoners from darkness, and proclaim the year of the Lords favor.
Thus, Jesus begins the ‘year of the Lords favor’ or the Messianic Age.