The quote is taken form the Whole Earth Catalog [1]. Jobs referenced it a lot the quote you are using is its first line. Its last line which is often attributed to Jobs is in fact the, "Stay hungry. Stay foolish."
The reference -- and the concern about tinkering with the tree of life -- goes a bit further back:
"And YHVH said, Behold, the man is become as one of us, to know good and evil; and now -- lest he put forth his hand, and take also of the tree of life, and eat, and live forever -- let us send him forth from the garden of Eden, to till the ground from whence he was taken. So he drove out the man; and he placed at the east of the garden of Eden Cherubim, and a flaming sword which turned every way, to keep the way of the tree of life." -- Genesis 3:22-3:24
(Nb.: Citation of religious text does not imply endorsement thereof.)
"And YHVH said, Behold, the man is become as one of us, to know good and evil; and now -- lest he put forth his hand, and take also of the tree of life, and eat, and live forever -- let us send him forth from the garden of Eden, to till the ground from whence he was taken. So he drove out the man; and he placed at the east of the garden of Eden Cherubim, and a flaming sword which turned every way, to keep the way of the tree of life." -- Genesis 3:22-3:24
(Nb.: Citation of religious text does not imply endorsement thereof.)