The idea that Abraham was alive, as an idea coming into this text is derived from these words of Jesus -
I speak what I have seen with My Father... John 8:38
What is it that Jesus has seen with His Father that would teach us Abraham is alive. He just got through telling the Pharisee's...You judge according to the flesh; John 8:15
In reading the previous book before John we see what Jesus has seen with the Father that is beyond the reasoning of the flesh -
As we see in Luke 16, a dialog between Abraham and the rich man
19 "There was a certain rich man who was clothed in purple and fine linen and fared sumptuously every day. 20 But there was a certain beggar named Lazarus, full of sores, who was laid at his gate, 21 desiring to be fed with the crumbs which fell from the rich man's table. Moreover the dogs came and licked his sores. 22 So it was that the beggar died, and was carried by the angels to Abraham's bosom. The rich man also died and was buried. 23 And being in torments in Hades, he lifted up his eyes and saw Abraham afar off, and Lazarus in his bosom. 24 Then he cried and said, 'Father Abraham, have mercy on me, and send Lazarus that he may dip the tip of his finger in water and cool my tongue; for I am tormented in this flame.' 25 But Abraham said, 'Son, remember that in your lifetime you received your good things, and likewise Lazarus evil things; but now he is comforted and you are tormented. 26 And besides all this, between us and you there is a great gulf fixed, so that those who want to pass from here to you cannot, nor can those from there pass to us.' 27 Then he said, 'I beg you therefore, father, that you would send him to my father's house, 28 for I have five brothers, that he may testify to them, lest they also come to this place of torment.' 29 Abraham said to him, 'They have Moses and the prophets; let them hear them.' 30 And he said, 'No, father Abraham; but if one goes to them from the dead, they will repent.' 31 But he said to him, 'If they do not hear Moses and the prophets, neither will they be persuaded though one rise from the dead.' " Luke 16:19-31
How could the rich man recognize Abraham afar off if Abraham has no form?
This is just one passage that Jesus displayed for us as He had seen with the Father, beyond the realm of the flesh.
Where one only see's that natural world and the things that live and die therein.
Because a person's body die's, does not mean they themselves are dead.
There is natural death of the human body and there is spiritual death of the human spirit and soul.
There is the first death and there is the second death.
To understand this is to rightly divide the word of truth.
JLB