Radak: It will never be thirsty.

Radak: It is streams of water.

Malbim: It is a place of harvest and fruits.

Rashi: The tree will not fear [harm]. Radak - this is an anthropomorphism. Even at a time of heat, there is no concern lest it dry. Even its leaves will be moist, and not fall, unlike other trees, whose leaves fall in winter.

Malbim: It will not fear constant evils, e.g. heat, nor sporadic evils, such as famines.

Rashi #1: It is hunger and famine.

Rashi #2: It is an expression of a fortified city. Also Menachem explained so.

Radak: It is when rain is withheld. Even then, it will not fear, for it is on water.

Rashi: It will not fear. Radak, Malbim - this is an anthropomorphism.

Radak: This is a parable for one who trusts in Hashem. His good will never depart, even when others are afflicted - "b'Shesh Tzaros Yatzileka uv'Sheva Lo Yiga Becha Ra" (Iyov 5:19). The fruits of a good man are his Chachmah and good deeds. His leaves are a metaphor for his wealth, from which people benefit.

Malbim: Just like the tree will not lose its fruits or leaves, one who trusts in Hashem will not lack his life and children, and not his wealth. Even though one may not engage in reproduction at a time of famine, as if he is too worried to make fruits, this man is not worried and will not cease making fruits.