The second part (vv. 19-37) draws out in detail, and at some points with heightened colouring, the fundamental prophecy by Nathan. It falls into two parts, of which the former (vv. 19-27) refers more especially to the promises given to David, and the second (vv. 28-37) to those relating to his descendants. In ver. 19 "vision" is quoted from 2 Sam. vii. 17; "then" points back to the period of giving the promise; "Thy favoured one," is possibly Nathan, but more probably David. The Masoretic reading, however, which is followed by many ancient versions, has the plural "favoured ones," which Delitzsch takes to mean Samuel and Nathan. "Help" means the help which, through the king, comes to his people, and especially, as appears from the use of the word "hero," aid in battle. But since the selection of David for the throne is the subject in hand, the emendation which reads for "help" _crown_ recommends itself as probable. David's prowess, his humble origin, and his devotion to God's service are brought into view in vv. 19, 20, as explaining and magnifying the Divine choice. His dignity is all from God. Consequently, as the next pair of verses goes on to say, God's protecting hand will ever be with him, since He cannot set a man in any position and fail to supply the gifts needed for it. Whom He chooses He will protect. Sheltered behind that strong hand, the king will be safe from all assaults. The word rendered "steal upon" in ver. 22 is doubtful, and by some is taken to mean _to exact_, as a creditor does, but that gives a flat and incongruous turn to the promise. For ver. 22 _b_ compare 2 Sam. vii. 10. Victory over all enemies is next promised in vv. 23-25, and is traced to the perpetual presence with the king of God's Faithfulness and Loving-kindness, the two attributes of which so much has been sung in the former part. The manifestation of God's character (_i.e._, His Name) will secure the exaltation of David's horn--_i.e._, the victorious exercise of his God-given strength. Therefore a wide extension of his kingdom is promised in ver. 25, from the Mediterranean to the Euphrates and its canals, on which God will lay the king's hand--_i.e._, will put them in his possession.
The next pair of verses (26, 27) deals with the inward side of the relations of God and the king. On David's part there will be child-like love, with all the lowliness of trust and obedience which lies in the recognition of God's fatherhood, and on God's part there will be the acknowledgment of the relation, and the adoption of the king as His "first-born," and therefore, in a special sense, beloved and exalted. Israel is called by the same name in other places, in reference to its special prerogative amongst the nations. The national dignity is concentrated in the king, who stands to other monarchs as Israel to other nations, and is to them "Most High," the august Divine title, which here may possibly mean that David is to the rulers of the earth an image of God. The reciprocal relation of Father and Son is not here conceived in its full inwardness and depth as Christianity knows it, for it has reference to office rather than to the person sustaining the office, but it is approximating thereto. There is an echo of the fundamental passage in ver. 26. (Compare 2 Sam. vii. 14.)
From ver. 28 onwards the psalmist turns to expand the promises to David's line. His words are mainly a poetical paraphrase of 2 Sam. vii. 14. Transgression shall indeed be visited with chastisement, which the fatherly relation requires, as the original passage indicates by the juxtaposition of the promise "I will be his Father," and the declaration "I will chasten him." But it will be chastisement only, and not rejection. The unchangeableness of God's loving purpose is very strongly and beautifully put in ver. 33, in which the twin attributes of Loving-kindness and Faithfulness are again blended as the ground of sinful men's hope. The word rendered above "break off" occasions a difficulty, both in regard to its form and its appropriateness in this connection. The clause is a quotation from 2 Sam. vii. 15, and the emendation which substitutes for _break off_ the more natural word used there--namely, _withdraw_--is to be preferred. In ver. 33 b the paradoxical expression of _being false to My faithfulness_ suggests the contradiction inherent in the very thought that He can break His plighted word. The same idea is again put in striking form in ver. 34: "I will not profane My covenant," even though degenerate sons of David "profane" God's statute. His word, once spoken, is inviolable. He is bound by His oath. He has given His holiness as the pledge of His word, and, till that holiness wanes, those utterances which He has sealed with it cannot be recalled. The certainty that sin does not alter God's promise is not traced here to His placableness, but to His immutable nature, and to the obligations under which He is laid by His own word and acts. That unchangeableness is a rock-foundation, on which sinful men may build their certitude. It is much to know that they cannot sin away God's mercy nor exhaust His gentle long-suffering. It is even more to know that His holiness guarantees that they cannot sin away His promises, nor by any breach of His commandments provoke Him to break His covenant.