Objection 4. Faith does not justify without that which is required in those who are justified. Good works are required in those who are justified. Therefore, faith is not without good works, and so does not justify alone.
Answer: There is here the same fallacy to which reference has just been made, on account of the doubtful construction of the particle without. Faith does not, indeed, justify without those things which are required in those who are justified. But although it never exists alone, and is always joined with love, by which it works, yet it alone justifies—is the act of embracing and applying to itself the merits of Christ. The minor also must be more fully explained; for faith and good works are not required in the same sense in those who are justified. Faith, with its own peculiar act, (without which it cannot be considered) is required as the necessary instrument, by which we apply to ourselves the merits of Christ. Good works, on the other hand, are not required that by them we may apprehend the merits of Christ, much less that we may be justified on account of them; but that we may thereby prove our faith, which without good works is dead, and can only be known by their presence.
Good works are required as the fruits of our faith, and as the evidences of our gratitude to God. That is not always necessary for the accomplishment of a certain result, which is necessarily connected with the cause of the same thing. So good works, although they are necessarily connected with faith, are nevertheless not necessary for the apprehension of the merits of Christ.
Zacharias Ursinus, Commentary on the Heidelberg Catechism, 337.