A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
2 Kings (2 Samuel) 7:2
sa2 7:2NATHAN APPROVES THE PURPOSE OF DAVID TO BUILD GOD A HOUSE. (Sa2 7:1-3)
the king said unto Nathan the prophet, See now, I dwell in an house of cedar--The palace which Hiram had sent men and materials to build in Jerusalem had been finished. It was magnificent for that age, though made wholly of wood: houses in warm countries not being required to possess the solidity and thickness of walls which are requisite for dwellings in regions exposed to rain and cold. Cedar was the rarest and most valuable timber. The elegance and splendor of his own royal mansion, contrasted with the mean and temporary tabernacle in which the ark of God was placed, distressed the pious mind of David.
2 Kings (2 Samuel) 7:3
sa2 7:3Nathan said to the king, Go, do all that is in thine heart--The piety of the design commended it to the prophet's mind, and he gave his hasty approval and encouragement to the royal plans. The prophets, when following the impulse of their own feelings, or forming conjectural opinions, fell into frequent mistakes. (See on Sa1 16:6; Kg2 4:27).
2 Kings (2 Samuel) 7:4
sa2 7:4GOD APPOINTS HIS SUCCESSOR TO BUILD IT. (Sa2 7:4-17)
it came to pass that night, that the word of the Lord came unto Nathan--The command was given to the prophet on the night immediately following; that is, before David could either take any measures or incur any expenses.
2 Kings (2 Samuel) 7:11
sa2 7:11Also the Lord telleth thee that he will make thee an house--As a reward for his pious purpose, God would increase and maintain the family of David and secure the succession of the throne to his dynasty. [See on Ch1 17:10].
2 Kings (2 Samuel) 7:12
sa2 7:12I will set up thy seed after thee, &c.--It is customary for the oldest son born after the father's succession to the throne to succeed him in his dignity as king. David had several sons by Bath-sheba born after his removal to Jerusalem (Sa2 5:14-16; compare Ch1 3:5). But by a special ordinance and promise of God, his successor was to be a son born after this time; and the departure from the established usage of the East in fixing the succession, can be accounted for on no other known ground, except the fulfilment of the divine promise.
2 Kings (2 Samuel) 7:13
sa2 7:13He shall build an house for my name, and I will establish the throne of his kingdom for ever--This declaration referred, in its primary application, to Solomon, and to the temporal kingdom of David's family. But in a larger and sublimer sense, it was meant of David's Son of another nature (Heb 1:8). [See on Ch1 17:14.]
2 Kings (2 Samuel) 7:18
sa2 7:18DAVID'S PRAYER AND THANKSGIVING. (Sa2 7:18-29)
Then went king David in, and sat before the Lord--Sitting was anciently an attitude for worship (Exo 17:12; Sa1 4:13; Kg1 19:4). As to the particular attitude David sat, most probably, upon his heels. It was the posture of the ancient Egyptians before the shrines; it is the posture of deepest respect before a superior in the East. Persons of highest dignity sit thus when they do sit in the presence of kings and it is the only sitting attitude assumed by the modern Mohammedans in their places and rites of devotion.
2 Kings (2 Samuel) 7:19
sa2 7:19is this the manner of man, O Lord God?--that is, is it customary for men to show such condescension to persons so humble as I am? (See Ch1 17:17.)
2 Kings (2 Samuel) 7:20
sa2 7:20what can David say more unto thee?--that is, my obligations are greater than I can express.