What does Psalm 22:8 mean?

This statement is being spoken in sarcasm, by David's taunting opponents. In a time where he feels abandoned by God (Psalm 22:1–2), part of his hardship is hearing others mock his pain (Psalm 22:6–7). Enemies laugh at his trust, suggesting it was unfounded. According to ungodly thinking, if David's trust in the Lord was valid, he would not be in this situation. Their words are intended to be insulting. All the same, these are part of a prophetic look at the experience of the Messiah (Matthew 27:46; Psalm 22:1).

As He died on the cross Jesus encountered the same sarcastic accusation from the religious leaders. They called out: "He trusts in God; let God deliver him now, if he desires him. For he said, 'I am the Son of God'" (Matthew 27:43). The two robbers who were crucified with Jesus also mocked Jesus' trust in the Lord. Matthew 27:44 says they "also reviled him in the same way."

Of course, Jesus' heavenly Father delivered Him out of death by raising Him to life on the third day. The ultimate conclusion of this psalm is that God will not eternally abandon those He loves (Psalm 22:22). In his address to the Jews at Pentecost the apostle Peter proclaimed Jesus as having been delivered up for crucifixion by "the definite plan and foreknowledge of God" and raised up by God (Acts 2:23–24).