Psalms 71:21

But this was discipline; admonition, not desertion. Lastly, giving thanks, he saith what? "And being turned Thou hast made me alive, and from the bottomless places of the earth again Thou hast brought me back." But when before? What is this "again"? Thou hast fallen from a high place, O man, disobedient slave, O thou proud against thy Lord, thou hast fallen. There hast come to pass in thee, "every one that exalteth himself shall be humbled:" may there come to pass in thee, "every one that humbleth himself shall be exalted." Return thou from the deep. I return, he saith, I return, I acknowledge; "O God, who is like unto Thee? How great troubles hast Thou shown to me, many and evil! and being turned Thou hast made me alive, and from the bottomless places of the earth again Thou hast brought me back." "We perceive," I hear. Thou hast brought us back from the bottomless places of the earth, hast brought us back from the depth and drowning of sin. But why "again"? When had it already been done? Let us go on, if perchance the latter parts of the Psalm itself do not explain to us the thing which here we do not yet perceive, namely, why he hath said "again." Therefore let us hear: "How great troubles Thou hast shown to me, many and evil! And being turned Thou hast made me alive, and from the bottomless places of the earth again Thou hast brought me back." What then? "Thou hast multiplied Thy righteousness, and being turned Thou hast comforted me, and from the bottomless places of the earth again Thou hast brought me back" (ver. 21). Behold a second "again"! If we labour to unravel this "again" when written once, who will be able to unravel it when doubled? […]

When our Lord Jesus was quickened again, and brought back from the depths of the earth, his greatness was increased, and he entered on the joy set before him.

Thou shalt increase my greatness,....

Thou shalt increase my greatness - Thou wilt restore me to my throne and kingdom; and it shall be done in such a way that all shall see it was the hand of God; and I shall have the more honor on the account. Comfort me on every side - I shall have friends in all quarters; and the tribes on all sides will support me.

Thou shalt increase my greatness - Thou wilt not merely restore me to my former condition, but wilt enlarge my happiness, and wilt do still greater things for me. And comfort me on every side - literally, “Thou wilt turn thyself; thou wilt comfort me.” The word also means to surround; to encompass Gen 2:11, Gen 2:13; 1Ki 7:24; Psa 18:5; and the idea here may be that God would “go around him,” or encircle him, and would thus comfort him. This idea is expressed in our common version. It was the confident assurance of entire, or complete consolation.