First century Christianity is unquestionably centered on the birth, life, death, burial, and resurrection of Jesus Christ to about 33 AD. The first thirty years were His private life and the next three and one-half years were His public life, which is encompassed by the four Gospels, Matthew, Mark, Luke, and John.
Just before Jesus ascended to heaven, He said:
But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth (Acts 1:8).
In the Acts of the Apostles, the Apostle Luke gives us the history of exactly how the disciples took the Gospel of Jesus Christ to Jerusalem, Judaea, Samaria and then on to Asia and Europe. This occurred from approximately 33 AD to 63 AD. The Book of Acts does not end in "Amen". Obviously God had not completed His work, as the Gospel of Jesus Christ is being preached around the globe today.
Those saved in the Gospels of Matthew, Mark, Luke and John were saved under the Old Covenant as the New Covenant did not come into effect until after Christ’s ascension (John 7:39; 16:7; Acts 1:4-8; Hebrews 9:14-17).
Those saved under the New Covenant, those who became born again believers on the day of Pentecost and throughout the Acts of the Apostles became saints in Christ's church. The Bible does not leave any other instructions on how to get to heaven than what we find written in the Acts of the Apostles. To become a saint in Christ's church today, we must do exactly what Christians did in the first century. This is the way to get to heaven!
I have personally read the New Testament, which obviously and completely describes first century Christianity, at least twenty times and I have never found the following in the Acts of the Apostles or anywhere in the New Testament:
The question clearly has to be, "how can this possibly be?" None of the above list is part of first century Christianity but most of the Christian world follows these non-Biblical practices. The answer is pretty obvious. The theology was put in place when the Christians and pagans were forced into a truce by King Constantine by the merging of God and state into the Roman Catholic Empire at the First Council of Nicaea in 325 AD. The doctrine was finalized as the Athanasian Creed sometime in the fifth century.
As the centuries past, these creeds became a "traditional" religion. The laity did not have Bibles to read until the 15th century so they accepted the teaching of their priests and Popes as the truth. The Protestant Reformation in the 15th century removed much of the Catholic tradition (items 14 to 27 above). The problem is that the reformists either kept some of Catholic tradition or added their own doctrine which form the first thirteen items on the list above. Now the Protestant doctrine over the centuries has become a new traditional religion. Similarly, the Latter Day Saints, the Seventh Day Adventists, Unitarians, Jehovah Witnesses, etc. developed their own doctrines in the nineteenth century by using some of the Protestant traditions and/or adding their own invented doctrine to spread and grow their false beliefs to millions of people around the world.
So simple! Don't be fooled by traditional religion! Obey the Gospel of Jesus Christ by obeying Acts 2:38. Millions around the world are leaving their traditional religions behind and becoming new creatures in Christ (2 Corinthians 5:17) by truly being born again and living and leading a repentant lifestyle.