Charles Spurgeon Commentary 1 Peter 2:3-4

"if ye have tasted that the Lord is gracious: unto whom coming, a living stone, rejected indeed of men, but with God elect, precious," — 1 Peter 2:3-4 (ASV)

If indeed you have tasted that the Lord is gracious. To whom coming, as to a living stone,

So "the Lord" mentioned here is the Lord Jesus Christ. He is truly "a living stone."