Psalm 92:14 They shall still bring forth fruit in old age; they shall be fat and flourishing;

The pronoun "they" is in reference to the "cedar and palm tree" (God's people). Where the house of God is built with cedars and palms are planted in it. When we are planted in the house of God, even in our old age, we will be "fat and flourishing". i.e. we will never stop being fruitful, as the root (Jesus) will not stop supplying us with spiritual surplus (fat)

Malachi 3:10 ......prove me now herewith, saith the Lord of hosts, if I will not open you the windows of heaven, and *pour you out a blessing, that there shall not be room enough to receive it.*

When we are planted in Christ, its inevitable that we will be fruitful and receive more than we have room to contain (fat). Therefore, all our days, we are to deliver to others what we have received of the Lord. We flourish to give glory to him who caused us to flourish, by giving to others so that they to can:

Romans 11:17 .....became a partaker of the root and fatness of the olive tree,