The tree of the knowledge of good and evil signifies Satan as the source of death to man (Heb. 2:14). It also signifies all things apart from God, for anything that is not God Himself, including good things and even scriptural things and religious things, can be utilized by Satan, the subtle one, to bring death to man. Even the Scriptures inspired by God and the law given by God can be utilized by Satan as the tree of knowledge to bring in death (John 5:39-40; 2 Cor. 3:6).
The tree of life causes man to be dependent on God (John 15:5), whereas the tree of knowledge causes man to rebel against God and to be independent from Him (cf. Gen. 3:5). The two trees issue in two lines — the line of life and the line of death — that run through the entire Bible and end in the book of Revelation. Death begins with the tree of knowledge (v. 17) and ends with the lake of fire (Rev. 20:10, 14). Life begins with the tree of life and ends in the New Jerusalem, the city of the water of life (Rev. 22:1-2).