I don't see in the Bible where Christians believed God was within you. God's Holy Spirit can dwell within you, but God the Father resides in heaven. God the Son appeared on earth;
Matthew 1:23 Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us.
Matthew 5:8 Blessed are the pure in heart: for they shall see God.
Matthew 5:9 Blessed are the peacemakers: for they shall be called the children of God.
There are many discriptions of "The Kingdom of God" as being a place in heaven. There is one reference of the Kingdom of God being in our hearts as something we should always keep before us knowing it is our final destination.
Luke 17:21 Neither shall they say, Lo here! or, lo there! for, behold, the kingdom of God is within you.
Mark 14:25 Verily I say unto you, I will drink no more of the fruit of the vine, until that day that I drink it new in the kingdom of God.
Matthew 22:30 For in the resurrection they neither marry, nor are given in marriage, but are as the angels of God in heaven.
John 14:2-3 In my Father's house are many mansions: if it were not so, I would have told you. I go to prepare a place for you. And if I go and prepare a place for you, I will come again, and receive you unto myself; that where I am, there ye may be also. (heaven)
First century Christians were all believers in a heavenly home. They also believed that at the moment of death they would go there.
1 Corinthians 15:44-49 It is sown a natural body; it is raised a spiritual body. There is a natural body, and there is a spiritual body. And so it is written, The first man Adam was made a living soul; the last Adam was made a quickening spirit. Howbeit that was not first which is spiritual, but that which is natural; and afterward that which is spiritual. The first man is of the earth, earthy: the second man is the Lord from heaven. As is the earthy, such are they also that are earthy: and as is the heavenly, such are they also that are heavenly. And as we have borne the image of the earthy, we shall also bear the image of the heavenly.
Jesus is a "quickening spirit" zwopoiew zoopoieo dzo-op-oy-eh'-o
to make alive, give life, the early Christians all believed they would be changed from the physical to the spirit, literally