Although the Old Law did not suffice to save man, yet another help from God besides the Law was available for man, viz. faith in the Mediator, by which the fathers of old were justified even as we were. [ST I-II Q98, A2, ad 4]And:
As to those under the Old Testament who through faith were acceptable to God, in this respect they belonged to the New Testament: for they were not justified except through faith in Christ, Who is the Author of the New Testament. [ST I-II Q107, A1, ad 3]Does the same hold true for us as it did for them? Yes:
It is written (Romans 5:1): "Being justified therefore by faith, let us have peace with God."Hence we see that those who claim that the Catholic Church teaches a works-based Gospel are badly misinformed.
I answer that, As stated above (3) a movement of free-will is required for the justification of the ungodly, inasmuch as man's mind is moved by God. Now God moves man's soul by turning it to Himself according to Ps. 84:7 (Septuagint): "Thou wilt turn us, O God, and bring us to life." Hence for the justification of the ungodly a movement of the mind is required, by which it is turned to God. Now the first turning to God is by faith, according to Heb. 11:6: "He that cometh to God must believe that He is." Hence a movement of faith is required for the justification of the ungodly. [ST I-II Q113, A4]