Jamieson, Fausset and Brown on Ezekiel 47:12

12. Instead of the "vine of Sodom and grapes of Gomorrah" (De 32:32), nauseous and unwholesome, trees of life-giving and life-restoring virtue shall bloom similar in properties to, and exceeding in number, the tree of life in Eden (Re 2:7; 22:2, 14).

leaf ... not fade--expressing not only the unfailing character of the heavenly medicine of the tree of life, but also that the graces of the believer (as a tree of righteousness), which are the leaves, and his deeds, which are the fruits that flow from those graces, are immortal (Psa 1:3; Jr 17:8; Mt 10:42; 1Co 15:58).

new fruit--literally, "firstlings," or first fruit. They are still, each month afresh, as it were, yielding their first-fruit [Fairbairn]. The first-born of a thing, in Hebrew idiom, means the chiefest. As Job 18:13, "the first-born of death," that is, the most fatal death.