וַיֹּ֥אמֶר דָּוִ֖ד לַאֲבִיגַ֑ל בָּר֤וּךְ יְהוָה֙ אֱלֹהֵ֣י יִשְׂרָאֵ֔ל אֲשֶׁ֧ר שְׁלָחֵ֛ךְ הַיּ֥וֹם הַזֶּ֖ה לִקְרָאתִֽי׃
And David said to Abigail: ‘Blessed be the LORD, the God of Israel, who sent thee this day to meet me;
Akeidat Yitzchak
Expulsion was necessary to maintain the nature of man. Had man's lifespan become unconditionally infinite through his eating from the tree of life, he would no longer have been a unique creature in the universe. He would have become a sub species of the celestial beings. By having to maintain a balance between the animalistic and the Divine, and by constantly having to face this challenge, he could remain human. Therefore, the gates of Eden had to remain closed to him.