He shall abide before the face of God for ever. This is only a simpler way of expressing what he had said before, I will abide in thy tabernacle for ever. He refers to the security and peace which he would enjoy under the protection of God, who would effectually preserve his life. By the face of God, must be meant the fatherly care and providence which he extends to his people. So numerous are the dangers which surround us, that we could not stand a single moment, if his eye did not watch over our preservation. But the true security for a happy life lies in being persuaded that we are under divine government. There follows a prayer that God would appoint mercy and truth for preserving the king. And this admits of two meanings. As clemency and truth are the best safeguards of a kingdom, it would not be altogether unreasonable to suppose that David prays here to be endued with these dispositions, as a means of establishing his throne. But the other meaning is perhaps preferable, that God would gird himself with clemency and truth in order to the preservation of the king. The Hebrew term mnh, manah, signifies not only to prepare, but to set over, or appoint; and he speaks as if the true defense of the kingdom was only to be found in the mercy and faithfulness of God. He uses the expression prepare, or command, to intimate how easily God can provide the means necessary for preserving his people. In the concluding words, he expresses his resolution to persevere in the constant celebration of the praises of God, with a view to fulfilling the vows which he had contracted -- and this again may lead us to remark the agreement which ought ever to subsist between the two parts of invocation: for David, while he applied to God for help, under the pressure of calamity, showed himself uniformly grateful when he had experienced deliverance.

He shall abide before God for ever - That is, perpetually; without danger of change, or of being driven into exile. This may allude, however, to the hope which David had that he would always live with God in a higher world - a world where there would be no danger of change or banishment. His restoration to his home, to his throne, and to the privileges of the sanctuary, he may have regarded as an emblem of his ultimate reception into a peaceful heaven, and his mind may have glanced rapidly from the one to the other. On earth, after his restoration, he would have no fear that he would be banished again; in heaven, of which such a restoration might be regarded as an emblem, there could be no change, no exile.
O prepare mercy and truth - literally, divide, or divide out; then, allot or appoint; and then, make ready or prepare. The prayer is, that God would measure out to him, or impart to him, such favor that this desire of his heart would be realized. On the phrase mercy and truth, see Psalm 25:10, note; Psalm 57:3, note; Psalm 57:10, note.
Which may preserve him - They will preserve him. That is, the manifestation of such mercy and truth would make his permanent occupancy of his throne on earth, and his ultimate reception into heaven, secure.

He shall abide before God for ever - Literally, "He shall sit for ever before the faces of God." He shall ever appear in the presence of God for us. And he ever sits at the right hand of the Majesty on high; for he undertook this office after having, by his sacrificial offering, made atonement for our sins.
Prepare mercy and truth, which may preserve him - As Mediator, his attendants will ever be mercy and truth. He will dispense the mercy of God, and thus fulfill the truth of the various promises and predictions which had preceded his incarnation. There is an obscurity in this clause, חסד ואמת מן ינצרהו chesed veemeth man yintseruhu, owing to the particle מן man, which some translate who or what; and others, number thou, from מנה manah, to count. Houbigant, and he is followed by Bishop Lowth, would read מיהוה miyehovah, Mercy and truth from Jehovah shall preserve him. The AngloSaxon has, Mildheartedness, and soothfastness his, who seeketh? which is nearly the rendering of the old Psalter: Mercy and sothfastnes of him, wha sall seke? Dr. Kennicott says, מן man is a Syriasm; and should be translated quaesoutinam, I beseech thee, - I wish, - O that! On this very ground Coverdale appears to have translated, O let thy lovynge mercy and faithfulnes preserve him! The sense I have given above I conceive to be the true one.

He shall abide before God for ever: O prepare (e) mercy and truth, [which] may preserve him.
(e) For the stability of my kingdom stands in your mercy and truth.

He shall abide before God for ever,.... Or "sit" (b); or "may he sit". Being raised from the dead he was received up to heaven into the presence of God, and sat down at his right hand; where he abides for ever, a Priest upon his throne, having an unchangeable priesthood, Hebrews 7:24;
and prepare mercy and truth, which may preserve him; which, if literally understood of David, is a prayer that the Lord would show him favour and kindness, and perform his promises to him, whereby his life would be preserved from the plots and, conspiracies of his enemies, and his kingdom be established; or that he might be exalted to exercise mercy towards his subjects, and administer justice, or execute the judgment of truth among them; which would make for the preservation of his person, and the support of his throne and government, Proverbs 20:28. But as the words may be applied to the Messiah, they are to be understood, not of the preservation of his corporeal life while here on earth; but either of the preservation of his people, in whom he lives, through the mercy and truth of God, expressed in the exertion of his power, by which they are preserved unto the heavenly kingdom and glory; or of the security of his kingdom, which not being of this world, is not supported by worldly power and policy, but in a spiritual manner, and by spiritual means; such as mercy, or "grace and truth"; that is, the doctrines of grace and truth, which came by Christ, and are preached by his ministers, and are the means of continuing, promoting, and preserving his kingdom and interest in the world, Or the words may be rendered, "may mercy and the truth of manna keep thee"; the true manna, Christ; see John 6:32; or "mercy and truth, as the manna, keep thee" (c); as that was kept in the golden pot, Exodus 16:33; or rather as that kept and sustained the Israelites in the wilderness.
(b) "sedebit", Tigurine version, Vatablus, Musculus, Cocceius, Michaelis; so Ainsworth; "vel sedeat", Vatablus, Gejerus, Amama. (c) Vid. Hackman. Praecidan. Sacr. tom. 1. p. 71.

abide before God--literally, "sit as a king in God's presence," under His protection.

Abide - In the throne. Before God - Living and ruling as in God's presence, serving God and worshipping him in his tabernacle. Truth - Thy truth in giving me those mercies which thou hast promised, and thy mercy in giving me such further blessings as I needs.