Who will live with God on the new earth and heaven that He creates for His children? This is a valid question and we know it is not only Christians. Some will be taken back, as I was when I first read this statement. However, I quickly realised that Abraham, Moses, Job, David would not strictly come into the category Christian.
“There was a man in the land of Uz whose name was Job, and that man was blameless and upright, one who feared God and turned away from evil.” Job 1:1
Think about the one thief upon the cross that simply asked Jesus to remember him when He came into His Kingdom, What was Jesus’ response?
“Truly, I say to you, today you will be with me in paradise.” Luke 23:43

I think therefore that the thief put his heartfelt trust in Jesus as the Messiah of God and that was enough to get him saved.
Roger Olson in his excellent article “Answer to the Question: What must a person know/believe to be saved or to be a Christian” raises the story of Paul and Silas and the time God opened up the prison doors for them. Paul stopped the jailor from killing himself as he thought the prisoners had escaped. The jailor knew there was something different about these men who had been praising God in their chains and were now free of those chains. He asked them this question.
“Sirs, what must I do to be saved?” And they said, “Believe on (trust) the Lord Jesus, and you will be saved, you and your household.” Acts 16:30-31
Roger makes the point that from this statement, for the jailer and his family to be saved they had to believe that Jesus Christ is Lord and they must put their trust/faith in Him. This is the simple rule of faith for salvation.
To be a Christian there is more and Roger points out that Paul and Silas then went on to say:
“And they spoke the word of the Lord to him and to all who were in his house.” Acts 16:32
Roger’s interpretation and I have to agree with him, is that the jailer, like the thief on the cross, was saved the moment he believed on (trust) the Lord Jesus Christ as his Lord. However, to be a Christian there is more, Jesus gave His disciples the Great Commission; repent, be baptised, and receive the Holy Spirit. The Holy Spirit enables believers to comprehend the Word of the Lord. He sanctifies us over time and produces the fruit of the Spirit in our lives. He will guide our every step if we allow Him. Therefore, He enables us to live the Christian life.
SAVED
God knows the condition of our heart and it is a heart issue that gets us saved. This Scripture from Exodus reinforces the issue of having a heart/spirit for God.
“And they came, every one whose heart stirred him, and everyone whose spirit moved him, and brought the Lord’s contribution to be used for the tent of meeting, and for all its service, and for the holy garments. So they came, both men and women. All who were of a willing heart brought brooches and earrings and signet rings and armlets, all sorts of gold objects, every man dedicating an offering of gold to the Lord.” Exodus 35:21-22
CHRISTIAN
To live the Christian life you must have the Holy Spirit which is given once you repent of your sins (prepared to die to your old life) be baptised (signifying death to the old life and arising as alive in Christ) at which time God the Father sends the Holy Spirit, the enabler, to be your counsellor, your teacher, and comforter. He enables you to live a Christian life.
ETERNITY
For me, this understanding gives me comfort in knowing that there will be many people who have never heard the Good News of Jesus Christ who will be saved because they had a heart after God. Moreover, I am sure you like me have heard of many stories of Jesus appearing to Muslims and they have come to saving faith in Him. Jesus answered their heart cries. We can trust God to ensure that all those that should be in His Kingdom will be there.