What does Psalm 24:4 mean?

The answer to the question posed in verse 3 is given here. Proper worship of God requires clean hands, a pure heart, and integrity. A person cannot truly worship God unless they are submitted to Him in faith, and that submission cannot occur until they have been redeemed by salvation. The question is not whether or not a person is capable of singing or saying words; it's whether their efforts are appropriate.

The Levites who transported the ark had to be ceremonially clean, as did the priests. Exodus 30:18–21 instructs Aaron, the high priest, and his sons to wash their hands and feet at the laver in the tabernacle before ministering to the Lord. Isaiah 52:11 commands: "Purify yourselves, you who bear the vessels of the LORD."

Having "clean hands" refers to the performance of righteous deeds, as well as avoidance of evil deeds. This imagery is reflected in modern English expressions such as "willing to get his hands dirty," which implies someone willing to do evil to accomplish their goals. Pilate's dramatic washing of his hands declared his opinion that he was completely innocent of what happened to Jesus (Matthew 27:24).

Having a pure heart likely refers to a person's godly thoughts and character. Further, the person who legitimately enters the Lord's presence in worship does not worship idols: anything or anyone other than the one true God.

A true worshipper does not practice deception (John 4:24). He is a person of integrity. The Lord cannot be fooled. He knows our thoughts, motives, deeds, and speech, and He hates hypocrisy. Jesus rebuked the scribes and Pharisees because they appeared righteous but were full of hypocrisy and lawlessness (Matthew 23:28).