How does the tree of life work?

Question

There were two special trees in Gan Eden. In the case of the tree of knowledge of good and bad, we know that eating from it once produced a permanent effect. Was this true for the tree of life too, or was that more like a "maintenance" tree that you had to keep eating from to live forever?

The reason I ask is that initially Adam and Chava were permitted to eat from that tree. Once they ate from the other, they were prevented from doing so. So either eating from the tree of life would also produce a permanent effect and it's just "luck" (as if there's any such thing in torah) that they didn't, or that tree works differently, like regular food where eating produces a temporary effect and eventually you need more. (Or, I suppose, that it produces a permanent effect that is cancelled by eating from the other tree.)

I searched this site and reviewed Rashi on B'reishit and my go-to source for English-language midrash, Sefer Ha-Aggadah, all without luck.

Answer 1

Zichron Yitzchok brings a dispute between those who hold that Odom was supposed originally to live forever (Shabbos 55b, Koheles Rabboh on Bereishis 3:18) but because of his sin, was condemned to die and those who hold that it is impossible to live forever (Ibn Ezra and others) and the punishment for eating the forbidden fruit must mean that he was condemned to die before his time.

Accordingly, the first opinion maintains that eating from the Tree of Life would allow Odom to regain his original state of immortality whilst the second opinion maintains that eating from that Tree would restore Odom's original longevity.

The Ramban gives a full explanation on pesukim 2:17 and 3:22 where Hashem says that after Odom had eaten from the Tree of Knowledge he could now eat from the Tree of Life and live forever. Ramban explains that originally, man did not have any inclination to do anything that his nature did not require him to do i.e. he would only do as he was commanded to do. Since he had no need to prolong his life he had no reason to eat from The Tree of Life. Once he had eaten from the Tree of Knowledge however, he had the motivation to eat from the Tree of Life (to regain his longevity or immortality) and he also had the capacity to defy Hashem's wishes to by succumbing to physical desire.

(The Ramban's own opinion seems to be clear where he says on (posuk 2:9) 'The Tree of Life is a tree whose fruit grants long life to whoever eats of it'.)

Answer 2

This is addressed by R. Isaiah of Trani (the Elder) in his commentary to Genesis 3:22.

ותימה וכי עד עתה לא אכל מעץ החיים והלא הרשה אותו מכל עץ הגן אכול תאכל יש לומר עץ החיים היא רפואה לעץ הדעת והרפואה מועלת לחולה לרפותו ולא להגן עליו שלא יחלה משל למי שישתה סם המות השקהו צרי וירפא אבל השקהו תחילה צרי ואחר כך השקהו סם המות ימות

This is astounding, for until now did he not eat from the Tree of Life? But was it not permitted to him – "from all the trees of the garden you may eat"?

We could answer that the Tree of Life is a remedy to the Tree of Knowledge, and the remedy helps the sick person to be healed but not to protect him from getting sick [in the first place]. This is analogous to someone who drinks poison – if they give him balm to drink he will be healed, but if they give him balm to drink first and then they give him poison to drink he will die.