This is a modified version of the Welsh tune from D. Emlyn Evans that is most commonly sung to the Augustus Toplady text, “A Debtor to Mercy Alone”:
A debtor to mercy alone, of covenant mercy I sing;
nor fear, with thy righteousness on, my person and off'ring to bring.
The terrors of law and of God with me can have nothing to do;
my Savior's obedience and blood hide all my transgressions from view.