By terrible things in righteousness wilt thou answer us, O God of our salvation; who art the confidence of all the ends of the earth, and of them that are afar off upon the sea:
-The manifestations of God's power to the uttermost parts of the earth are a ground of confidence to His praying people.
Verse 5 (By) terrible things in righteousness wilt thou answer us O God of our salvation ie Thou in Verse 5. (By) terrible things in righteousness wilt thou answer us, O God of our salvation - i:e., Thou, in accordance with that righteousness whereby thou dust give everyone his due (Deuteronomy 32:4), answerest our prayers in trouble, by vouchsafing to us marvelous deliverances, terribly displaying thy power against thy people's foes, as in Egypt, and at the Red Sea, and in Canaan. Compare Deuteronomy 10:21 and David's own phrase, 2 Samuel 7:23, "God went ... to do for you great things and terrible."
Who art the confidence of all the ends of the earth. God's display of His terrible power in behalf of His people will ultimately have the effect of so impressing all nations that they will join themselves to the Lord (Isaiah 66:16; Isaiah 66:18; Isaiah 66:23). God is in Himself potentially "the confidence of all the ends of the earth." Hereafter he will be recognized by all to be so (Psalms 22:27-28), of which the Queen of Sheba's coming to Solomon "from the uttermost parts of the earth" is a type (Matthew 12:42).
And of them that are afar off upon the sea - dwelling in distant maritime regions and islands.
Verse 6. Which by his strength setteth fast the mountains; being girded with power. His omnipotence is shown in His giving the mountains their unshaken security. "Mountains" are also the symbols of the elevated powers of the earth, kingdoms and dynasties (cf. end of Psalms 65:7; Psalms 46:3; Jeremiah 51:25).
Verse 7. Which stilleth the noise of the seas, the noise of their waves, and the tumult of the people. The sea is the emblem of the world-power (Psalms 46:2; Psalms 89:9; Daniel 7:2). In Jeremiah 5:22-24, as here, the stilling of the sea is joined with the harvest blessings, as manifesting the power of God, and calling for fear and thanksgivings on our part. God stilled Pharaoh's ocean-like rage against Israel; as also the Assyrian Sennacherib's against Jerusalem.
Verse 8. They also that dwell in the uttermost parts are afraid at thy tokens - for instance, thy thunders (cf. Psalms 65:5), the tokens or evidences of God's power and majesty, well calculated to inspire the beholders with reverential awe.
Thou makest the outgoings of the morning and evening to rejoice -- so that thou dost inspire with joy and love as well as with fear. "The outgoings of the morning and evening" are the east and the west-the points in the sky from which the morning and evening go out - i:e., the dwellers in the east and in the west; answering to the parallel, 'They that dwell in the uttermost parts.'