12 “All they that are in the circuit of Him shall offer gifts.” Who are in the circuit of Him?...Whatever is common to all is in the midst. Why is it said to be in the midst? Because it is at the same distance from all, and at the same proximity to all. That which is not in the middle, is as it were private. That which is public is set in the middle, in order that all they that come may use the same, may be enlightened. Let no one say, it is mine: lest he should be wanting to make his own share of that which is in the midst for all.
What then is, “All they that are in the circuit of Him shall offer gifts”? All they that understand truth to be common to all, and who do not make it as it were their own by being proud concerning it, they shall offer gifts; because they have humility: but they that make as it were their own that which is common to all, as though it were set in the middle, are endeavouring to lead men astray to a party, these shall not offer gifts....“To Him terrible.” Let therefore all men fear that are in the circuit of Him.
For therefore they shall fear, and with trembling they shall praise; because they are in the circuit of Him, to the end that all men may attain unto Him, and He may openly meet all, and openly enlighten all. This is, to stand in awe with others. When you have made him as it were your own, and no longer common, you are exalted unto pride; though it is written, “Serve ye the Lord in fear, and exult unto Him with trembling.” Therefore they shall offer gifts, who are in the circuit of Him. For they are humble who know truth to be common to all.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)