He shall cry unto me, Thou art my Father - He shall appeal to me, or come to me as a Father, and as his only hope and defense.
My God - He shall come to me as God, and shall recognize me as his God, his only trust and hope.
And the rock of my salvation - See the notes at Psalm 18:2. The meaning of all this is, that he would at all times recognize him as his only trust and hope, and that he would be faithful on his part to God.
“I have sworn unto David My servant ... with whom My hand shall be established: Mine arm also shall strengthen him.... My faithfulness and My mercy shall be with him: and in My name shall his horn be exalted. I will set his hand also in the sea, and his right hand in the rivers. He shall cry unto Me, Thou art my Father, my God, and the Rock of my salvation. Also I will make him My first-born, higher than the kings of the earth. My mercy will I keep for him forevermore, and My covenant shall stand fast with him.” Psalm 89:3-28. PP 755.1
“His seed also will I make to endure forever,
And his throne as the days of heaven.” Psalm 89:29. PP 755.2
“He shall judge the poor of the people,
He shall save the children of the needy,
And shall break in pieces the oppressor.
They shall fear thee while the sun endureth,
And so long as the moon, throughout all generations....
In his days shall the righteous flourish;
And abundance of peace, till the moon be no more.
He shall have dominion also from sea to sea,
And from the river unto the ends of the earth.”
“His name shall endure forever:
His name shall be continued as long as the sun:
And men shall be blessed in him:
All nations shall call him blessed.” PP 755.3