aka "There Is a Fountain Filled with Blood" or "Praise for the Fountain Opened". The hymn Cowper published in his 1779 hymnal, Olney Hymns, was called "Praise for the Fountain Opened" but became known by the first line - "There is a fountain filled with blood".
First verse - There is a fountain filled with blood Drawn from Immanuel's veins; And sinners, plunged beneath that flood, Lose all their guilty stains: Lose all their guilty stains, Lose all their guilty stains; And sinners, plunged beneath that flood, Lose all their guilty stains.