The term “Koine Greek” may be something you have heard but may be unsure as to its exact meaning and importance.
The Greek adjective koinos (from which koine is derived) denotes the idea of “common or belonging to several”; it stands in contrast to something which is unique or individually owned.
The phrase “Koine Greek” is designed to emphasize the fact that the Greek language used by the New Testament writers was the language of the common man in the first century A. D. Because of the worldwide conquest of Alexander the Great in the fourth century B. C., the Greek language had become the language of the world by the beginning of the third century B. C. and remained the lingua franca throughout the first century A. D.
Just as a nation’s coin is common currency among its people, so Koine Greek was the common linguistic currency among earth’s inhabitants during the writing of the New Testament. This is most important to know because it clearly demonstrates how earnestly God genuinely desired all people in the first century A. D. to be saved and to come to the knowledge of the truth (1 Timothy 2:3-4).
When Jude uses the word koinos in verse 3, he uses it to describe that salvation God desires for all people. A “common salvation” indicates that people of all races, nationalities, and cultures are saved by the same acts of obedience—faith in God and the gospel (Hebrews 11:6), repentance which turns away from sin and to Jesus (Luke 13:3, 5), confession of faith in Christ, the Son of God (Acts 8:37: Romans 10:9), and baptism for the remission of sins (Acts 2:38; Mark 16:16).
God has no unique or individual plan of salvation for you or a small sect of people. We are all called by the one gospel to faith in the one God and obedience to the one Lord via the one faith and the one baptism. This obedience adds us to the one body (i.e. the church) and gives all the one hope as we read and heed the word of God which was revealed and inspired by the one Spirit. This is what you must do to call upon the Lord and enjoy the common salvation of which Jude wanted to write more about.
Your conception and birth are according to God’s physical laws of procreation, and thus you share a common heritage with the rest of humanity. In like manner, your spiritual conception and birth are according to God’s spiritual laws of regeneration. Thus, you share a common salvation with all those who have likewise been are called out of the world by the gospel.