This is a little known but beautiful hymn by Isaac Watts.
The law and gospel distinguished.
1 The law commands, and makes us know
What duties to our God we owe;
But ’tis the gospel must reveal
Where lies our strength to do his will.
2 The law discovers guilt and sin,
And shews how vile our hearts have been;
Only the gospel can express
Forgiving love and cleansing grace.
3 What curses doth the law denounce
Against the man that fails but once!
But in the gospel Christ appears
Pardoning the guilt of numerous years.
4 My soul, no more attempt to draw
Thy life and comfort from the law,
Fly to the hope the gospel gives;
The man that trusts the promise lives.