They that trust in the Lord - His people; his friends. It is, and has been always, a characteristic of the people of God that they trust or confide in him.
Shall be as mount Zion - The mountain which David fortified, and on which the city was at first built, 2 Samuel 5:6-9. The name Zion became also the name by which the entire city was known.
Which cannot be removed, but abideth for ever - A mountain is an emblem of firmness and stability; and it is natural to speak of it as that which could not be removed. There is something more than this, however, intended here, as there is some ground of comparison especially in regard to Mount Zion. This must have been either the idea that Zion was particularly strong by position, or that it was under the divine protection, and was therefore safe. Most probably it refers to Zion as a place secure by nature, and rendered more so by art.