Psalm 52:8-9 But I am like a green olive tree in the house of God: I trust in the mercy of God for ever and ever. I will praise thee for ever, because thou hast done it: and I will wait on thy name; for it is good before the saints.
David responds to the evil deeds of unbelievers around him, like Doeg, who killed God’s priests, and like those who trust in the abundance of riches. His response was to become weak and tender like a green tree and be dependent on God’s mercy. His trust would be in God forever, unfailingly. He would then praise God for what He has done. He would wait in faith for God to act. He believed God and made himself dependent on the Lord.
In some sense it is easier for us NT believers to respond with such trust and praise and waiting, for the Lord has already acted decisively for us in the person and work of Jesus Christ. We believe God and trust in the Gospel of deliverance and salvation. Therefore, we can always praise the Lord and wait upon Him. This is true for us today and it is true forever.