Galatians 2:16

King James Version (KJV)

16Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified. 

Notice how he repeatedly says here, "faith OF Christ". Not "by faith IN Christ". He is not speaking about believing in Christ. That is assumed. He is speaking about the observance of the rituals instituted by Christ in His new way. He is speaking of the Sacraments.
And this, is Luther's error. He did not connect the Sacramental teaching of St. Paul. Luther recognized the Sacraments and he recognized the perfection of the sinner in the justification by faith. But denied the merit of that expression of faith in good works without which no one will be saved. And he applied St. Paul's teaching wrongly across the board. He failed to recognize the difference between the justification (i.e. perfection) that occurs as a result of the effort of the man of God:
2 Peter 1:4-10

King James Version (KJV)
4Whereby are given unto us exceeding great and precious promises: that by these ye might be partakers of the divine nature, having escaped the corruption that is in the world through lust.
5And beside this, giving all diligence, add to your faith virtue; and to virtue knowledge;
6And to knowledge temperance; and to temperance patience; and to patience godliness;
7And to godliness brotherly kindness; and to brotherly kindness charity. 8For if these things be in you, and abound, they make you that ye shall neither be barren nor unfruitful in the knowledge of our Lord Jesus Christ. 9But he that lacketh these things is blind, and cannot see afar off, and hath forgotten that he was purged from his old sins. 10Wherefore the rather, brethren, give diligence to make your calling and election sure: for if ye do these things, ye shall never fall.

It is ironic, those who reject the Sacraments will be judged by their works.

We who accept the Sacraments are saved by faith APART FROM OUR WORKS, when we receive the LAST RITES.

Sincerely,

De Maria