This is an excerpt from Martin Luther’s Commentary on Saint Paul’s Epistle to the Galatians (1535), written by Martin Luther and translated by Haroldo Camacho (1517 Publishing, 2018).
You say: Since forgiveness depends on faith alone, why must one nonetheless do good works? Answer: If faith is of the true sort, it cannot be without good works, just as no good work can be where unbelief dwells.