Albert Barnes Commentary 1 Kings 6:12

"Concerning this house which thou art building, if thou wilt walk in my statutes, and execute mine ordinances, and keep all my commandments to walk in them; then will I establish my word with thee, which I spake unto David thy father." — 1 Kings 6:12 (ASV)

The meaning is this: "As far as this house is concerned, you are obedient (2 Samuel 7:13; 1 Chronicles 17:12, and elsewhere); if you will be obedient in other things also, then I will fulfill My word." This shows that God’s promises are always conditional. The promises made to David were:

1. that he would be succeeded by one of his sons (2 Samuel 7:12; Psalms 132:11);
2. that the kingdom would be established in the line of his descendants forever, if they were faithful (Psalms 132:12); and
3. that the Israelites would be no more afflicted as before (2 Samuel 7:10).

These promises were now confirmed to Solomon, but on the express condition of obedience, and two further promises were added.