If we are going to be spiritually healthy, we need all the encouragement and support we can get. And in this section our "trainer" is telling us that spiritual fitness calls for team effort. Yes, we are to be oaks of righteousness, but God desires us not to be isolated oaks but growing "groves" of oaks, as is so well illustrated in nature by the giant sequoia trees of California that tower up to 300 feet.
These beautiful behemoths belie their unusually shallow root systems that reach out in all directions to capture the greatest amount of surface moisture. As their roots extend horizontally, the intertwining roots of the juxtaposed trees weave a network of support which provides stability against violent storms (think "storms of life").
In short, these gentle giants are so constructed by their Creator that they need each other, which explains why you virtually always see them growing assembled together in clusters ("not forsaking their assembling together"). Seldom do you see a Giant Redwood standing alone, because the high winds would quickly uproot the shallow root system of these "loners".
Because of the opposition to "The Way", the believers of the first century desperately needed to grow in groves and we of the 21st century are no different!
Christian fellowship provides us
With encouragement and love;
It will help us in our journey,
Till we reach our home above.
-- Precept Austin