Grace, triumphant in the throne,
Scorns a rival, reigns alone;
Come and bow beneath her sway;
Cast your idol works away!
Works of man, when made his plea,
Never shall accepted be;
Fruits of pride (vainglorious worm!)
Are the best he can perform.

Self, the god his soul adores,
Influences all his powers;
Jesus is a slighted name,
Self-advancement all his aim:
But when God the Judge shall come,
To pronounce the final doom,
Then for rocks and hills to hide
All his works and all his pride!

Still the boasting heart replies,
What the worthy and the wise,
Friends to temperance and peace,
Have not these a righteousness?
Banish every vain pretence
Built on human excellence;
Perish everything in man,
But the grace that never can.

William Cowper

http://www.poemhunter.com/poem/olney-hymn-63-not-of-works/