New Defender's Study Bible Notes
50:1 The mighty God, even the LORD. “The mighty” is actually a name of God—that is El; “God” is Elohim; “the LORD” is Jehovah or Yahweh. Thus, God under three names—El, Elohim, and Jehovah—reflecting the Triune Godhead, is here seen as summoning His entire creation to a great assembly, probably referring (Psalm 50:4) to the great judgment day (Revelation 20:11-15).
50:5 my saints. At the great judgment, all the “saints,” those who have come under the New Covenant by the sacrifice of Christ for their sins, will be gathered together unto the Lord. They will not be judged at this last great judgment, for Christ has already borne their judgment (Romans 8:1).
50:12 the world is mine. This is another assertion that the entire earth as well as all its living creatures (e.g., Psalm 50:10-11) belong to God as their Creator. No man really owns anything that has not been loaned him, as it were, by God, who expects an accounting some day (I Corinthians 4:7).
50:16 unto the wicked. The “wicked” are simply those who “forget God” (Psalm 50:22). They may, at the judgment, seek to offer their works as tantamount to “tak[ing] my covenant” (Psalm 50:16), but no one can be saved by works, and even their “righteousnesses are as filthy rags” (Isaiah 64:6), not to mention their many overt sins against God, which will be recounted at the judgment (Revelation 20:13).
50:23 shew the salvation. The Lord offers a final invitation to those yet living, before they have to come to the final judgment.