Albert Barnes Commentary 2 Kings 19:34

"For I will defend this city to save it, for mine own sake, and for my servant David`s sake." — 2 Kings 19:34 (ASV)

For my own sake - God’s honor was concerned with defending His own city against one who denied His power in direct terms, as Sennacherib did (2 Kings 18:35; 2 Kings 19:10–12). His faithfulness was also concerned with keeping the promise made to David (Psalms 132:12–18).