II Corinthians 5:17
“Therefore if any man be in Christ, he is a new creature: old things are passed away behold all things are become new.” (KJV)
“Therefore, if anyone is in Christ, he is a new creation; the old has gone, the new has come!” (NIV)
First, there’s something quite interesting about the use of verb tenses in this verse.
With the first verb “passed away,” the tense is what is called “aorist,” which means that “it points back to a definite moment or event.” In this case, it refers to the experience of the new birth. Everything that was associated with the old life – “distinctions, prejudices, misconceptions, and enslavements of the former unregenerated way of life – assume the character of pastness.”
A different tense is used for the words “become new.” Now the tense is “perfect active indicative”, which indicates that “the old things became and continue to be new; for the newness of God’s new creation is not a newness that in course of time palls and grows old and outmoded,” it is a newness that is continues to become new. (New International Commentary on the New Testament, II Corinthians, Philip Hughes, p.203) As Robertson puts it, they “. . . have become new to stay so.”
source: Change - II Corinthians 5:17
I hope it helps.