When King David compares the righteous man to the blossoming date tree (Tehillim
92:13), the full meaning of this metaphor can only be appreciated by contrasting it to an earlier comparison (ibid. 92:8) of the enemies of G-d to the grass sprouting from the earth. In his commentary on this psalm, Rabbi Avraham Ibn Ezra notes that the enemies to which the psalmist refers are the enemies of the righteous man who are likewise considered enemies of G-d. Although these enemies proliferate like blades of grass they are doomed to soon wither like the grass. The righteous, on the other hand, are comparatively few in number like the date tree but are blessed with the durability of that tree.
Elsewhere our Sages comment on the psalmist’s comparison of the righteous man to both the date tree and the cedar. Their explanation (Bava Batra 80b) is that the comparison to the date tree is to convey that just as that tree yields fruit, so do the good deeds of a righteous man yield fruits of reward for him in the World to Come. And just as the cedar has the ability to grow back after being cut, so the righteous have the ability to bounce back after every setback.