Asaph, having come to his senses in verses 13-15 on the foolishness of thinking the wicked will prosper realizes why when he considers and comes to God in his holy abode. That God is a greater treasure than all that could be given because God is eternal. 

So he realizes that God will receive and into glory even as he counsels him now in this life. 

He comes to realize that God is the strength of his heart and not himself and therefore we are brought back to verse one, knowing that God is good to those who are pure in heart. 

We are pure because we have been brought near to God by the very blood of Christ our a Lord as St. Paul writes in Ephesians 1. 

For this we thank and praise and serve and obey him as we confess his name and his promise through Jesus Christ.