So shalt thou say unto my servant David Lest David should be discouraged, or judge himself neglected of God, as one thought unworthy of so great an honour, God here gives him the honourable title of his servant, thereby signifying that he accepted of his service and good intentions.
Related Commentaries of 2 Samuel 7:8
2 Samuel 7:8
8 Now therefore so shalt thou say unto my servant David, Thus saith the LORD of hosts, I took thee from the sheepcote, from followingb the sheep, to be ruler over my people, over Israel: