Note: following the posting of the second half of the Psalm from J Forbes (1854) here is a broad pattern of the first half of the Psalm.

Maschil of Ethan the Ezrahite.

A. Promises to David
1 I will sing of the mercies of the LORD for ever:
with my mouth will I make known thy faithfulness to all generations.
2 For I have said, Mercy shall be built up for ever:
thy faithfulness shalt thou establish in the very heavens.
3 I have made a covenant with my chosen,
I have sworn unto David my servant,
4 Thy seed will I establish for ever,
and build up thy throne to all generations. Selah.

B. The saints praise YHWH
5 And the heavens shall praise thy wonders, O LORD:
thy faithfulness also in the congregation of the saints.
6 For who in the heaven can be compared unto the LORD?
who among the sons of the mighty can be likened unto the LORD?
7 God is greatly to be feared in the assembly of the saints,
and to be had in reverence of all them that are about him.
8 O LORD God of hosts, who is a strong LORD like unto thee?
or to thy faithfulness round about thee?

C. The Authority of the Creator
a. 9 Thou rulest the raging of the sea:
when the waves thereof arise, thou stillest them.
10 Thou hast broken Rahab in pieces, as one that is slain;
thou hast scattered thine enemies with thy strong arm.

b. 11 The heavens are thine, the earth also is thine:
as for the world and the fulness thereof, thou hast founded them.
12 The north and the south thou hast created them:
Tabor and Hermon shall rejoice in thy name.

a’. 13 Thou hast a mighty arm:
strong is thy hand, and high is thy right hand.
14 Justice and judgment are the habitation of thy throne:
mercy and truth shall go before thy face.

B’. The saints praise YHWH
15 Blessed is the people that know the joyful sound:
they shall walk, O LORD, in the light of thy countenance.
16 In thy name shall they rejoice all the day:
and in thy righteousness shall they be exalted.
17 For thou art the glory of their strength:
and in thy favour our horn shall be exalted.
18 For the LORD is our defence;
and the Holy One of Israel is our king.

A’. Promises to David
19 Then thou spakest in vision to thy holy one,
and saidst, I have laid help upon one that is mighty;
I have exalted one chosen out of the people.
20 I have found David my servant;
with my holy oil have I anointed him:
21 With whom my hand shall be established:
mine arm also shall strengthen him.
22 The enemy shall not exact upon him;
nor the son of wickedness afflict him.
23 And I will beat down his foes before his face,
and plague them that hate him.
24 But my faithfulness and my mercy shall be with him:
and in my name shall his horn be exalted.
25 I will set his hand also in the sea,
and his right hand in the rivers.
26 He shall cry unto me, Thou art my father,
my God, and the rock of my salvation.
27 Also I will make him my firstborn,
higher than the kings of the earth.

Note: John Forbes in 1854 -“The Symmetrical Structure of Scripture” – Kessinger Legacy Reprints,- draws attention to “a remarkable instance of a series of introverted parallelisms formed by verses, not lines”. He gives these two examples.  The correspondence  is based on contrasts as well as sometimes matching words. So in verse 30 even if David’s children forsake God, God is still faithful (v35). If they break the covenant (v31), God will not (v34).

A. 28 My mercy will I keep for him for evermore,
and my covenant shall stand fast with him.

B. 29 His seed also will I make to endure for ever,
and his throne as the days of heaven.

C. 30 If his children forsake my law,
and walk not in my judgments;

D. 31 If they break my statutes,
and keep not my commandments;

E. 32 Then will I visit their transgression with the rod,  and their iniquity with stripes.

E’. 33 Nevertheless my lovingkindness will I not utterly take from him, nor suffer my faithfulness to fail.

D’. 34 My covenant will I not break,
nor alter the thing that is gone out of my lips.

C’. 35 Once have I sworn by my holiness
that I will not lie unto David.

B’. 36 His seed shall endure for ever,
and his throne as the sun before me.

A’. 37 It shall be established for ever as the moon,
and as a faithful witness in heaven. Selah.

A. 38 But thou hast cast off and abhorred,
thou hast been wroth with thine anointed.

B. 39 Thou hast made void the covenant of thy servant:
thou hast profaned his crown by casting it to the ground.

C. 40 Thou hast broken down all his hedges;
thou hast brought his strong holds to ruin.

D. 41 All that pass by the way spoil him:
he is a reproach to his neighbours.

D’. 42 Thou hast set up the right hand of his adversaries;
thou hast made all his enemies to rejoice.

C’. 43 Thou hast also turned the edge of his sword,
and hast not made him to stand in the battle.

B’. 44 Thou hast made his glory to cease,
and cast his throne down to the ground.

A’. 45 The days of his youth hast thou shortened:
thou hast covered him with shame. Selah.