For God so loved the world, that He gave His only begotten Son, that whoever believes in Him shall not perish, but have eternal life.
What is this eternal life?
This is eternal life, that they may know You, the only true God, and Jesus Christ whom You have sent.
The word know used here is the same know that was used in Genesis, Adam knew Eve and Eve bore a son. It is that fellowship with internal understanding of someone. So the eternal life that Jesus got us by his death and resurrection is to fellowship with God for eternity. So we, who never gave Glory to God though his presence was evident via every creation, have been invited to fellowship with God. So we, who have no right to enter the tabernacle, are invited into the most holy place by the splitting of veil. What an amazing gift that God has given us for our faith in Jesus. So it is a gift that God gave us and we did not do anything to deserve this.
But in John 17-3 Jesus did not mention the start time of this fellowship nor the end time of fellowship. Then why is this thought that we will spend eternity with God ONLY after death? All this eternal security after death is a lie of devil. So the start time of this fellowship is from the time you believe in Jesus, if not it can be even from today, when you heard this truth. If it is not experienced today then how can this fellowship suddenly start after death? Brothers and sisters, I am not trying to disturb your theology of eternal security, but what I am trying to say is the full promise of Jesus does not have a starting point which means we can have the joy of fellowshipping with God right from now till eternity. Jesus was in this fellowship when he was on this earth in the likeness of man, so we can also have it.
Fellowship is something that needs to be experienced every day. For example if I attend any earthly fellowship (a gathering) one day and then failed to attend them thereafter, am I still part of that fellowship? Certainly not. Only those who are in the fellowship every single day will be considered a part of it. So this eternal fellowship with God also should be experienced every day. How do we know that we are in this eternal fellowship? By having a clear conscience with God or in other words by living a blameless life. If we have known sin in our life then we are not blameless, we have blame. The Holy Spirit in us is not pleased with this sin in us and so our conscience is not straight with God. What do we need to do in that case, we need to repent again just like what we did when we first entered the most holy place to enter the fellowship again. God is faithful enough to welcome us again. So it is not God who is rejecting us, but it is we who fail to act in a worthy manner to have fellowship with him. God is light and no darkness can have fellowship with light. That is why we become unworthy when we sin and have darkness in our life.
Having a clear conscience before God, is a sign that we have fellowship with God, Adam hid himself from God when his conscience was not clear before God in the garden of Eden after eating the forbidden fruit. But having a clear conscience or being blameless is not everything that you experience in this fellowship. To be in this fellowship is to submit everything that we have to God and to let God plan our life. John 17-10:- and all things that are Mine are Yours, and Yours are Mine; and I have been glorified in them. We need to live this life for God to mightily use us for his purpose. This includes letting God decide every single thing in your life. Jesus did that and that is why God used him mightily and Glorified him above all names.