John Gill Commentary 2 Samuel 7:27

"For thou, O Jehovah of hosts, the God of Israel, hast revealed to thy servant, saying, I will build thee a house: therefore hath thy servant found in his heart to pray this prayer unto thee." — 2 Samuel 7:27 (ASV)

For you, O Lord of hosts, God of Israel As he is called in (2 Samuel 7:26):

has revealed to your servant; which he otherwise could not have known:

saying, I will build you an house; see (2 Samuel 7:11);

therefore has your servant found in his heart to pray this prayer unto you; found his heart disposed to this service, or found freedom and boldness in him to put up this prayer to God; what encouraged and emboldened him to do it was the gracious promise of God, that he would build up his family, and establish his kingdom; or otherwise he could not have taken such liberty, and used such boldness with God in prayer, as to have requested it of him.