I can't say I know the answer to this question but here are biblical verses that could be used to argue that eternal life was not a gift from God prior to Jesus' sacrifice on the cross.
Genesis 3:22
22 And the Lord God said, “The man has now become like one of us, knowing good and evil. He must not be allowed to reach out his hand and take also from the tree of life and eat, and live forever.”
Ecc 3:18-22
18 I also said to myself, “As for humans, God tests them so that they may see that they are like the animals. 19 Surely the fate of human beings is like that of the animals; the same fate awaits them both: As one dies, so dies the other. All have the same breath[
c]; humans have no advantage over animals. Everything is meaningless. 20 All go to the same place; all come from dust, and to dust all return. 21 Who knows if the human spirit rises upward and if the spirit of the animal goes down into the earth?”
John 6: 67-69
67 So Jesus asked the Twelve, “Do you want to leave too?”
68 Simon Peter replied, “Lord, to whom would we go? You have the words of eternal life.
69We believe and know that You are the Holy One of God.”
John 4:7-13
7 When a Samaritan woman came to draw water, Jesus said to her, “Will you give me a drink?” 8 (His disciples had gone into the town to buy food.)
9 The Samaritan woman said to him, “You are a Jew and I am a Samaritan woman. How can you ask me for a drink?” (For Jews do not associate with Samaritans.
10 Jesus answered her, “If you knew the gift of God and who it is that asks you for a drink, you would have asked him and he would have given you living water.”
11 “Sir,” the woman said, “you have nothing to draw with and the well is deep. Where can you get this living water? 12 Are you greater than our father Jacob, who gave us the well and drank from it himself, as did also his sons and his livestock?”
13 Jesus answered, “Everyone who drinks this water will be thirsty again, 14 but whoever drinks the water I give them will never thirst. Indeed, the water I give them will become in them a spring of water welling up to eternal life.”