...a person is justified not by the works of the law but through faith in Jesus Christ.
That is to say, we don't win God's favor with a long resume of religious exertions or good deeds - we have it because it rests on the Son of God, to whom we belong by faith.
The Anglican Articles of Religion (1549) say,
XI. Of the Justification of Man.
We are accounted righteous before God, only for the merit of our Lord and Saviour Jesus Christ by Faith, and not for our own works or deservings. Wherefore, that we are justified by Faith only, is a most wholesome Doctrine, and very full of comfort, as more largely is expressed in the Homily of Justification.
A Doctrine "full of comfort," as we see in tomorrow's Gospel,
...a woman in the city, who was a sinner... stood behind Jesus at his feet, weeping, and began to bathe his feet with her tears... Then turning toward the woman, he said... "Do you see this woman? ...I tell you, her sins, which were many, have been forgiven; hence she has shown great love."
Justification by faith in Christ is comforting because it is available to any and all. Nameless, marginalized "sinners" can claim it just as much as the well known, well respected and religious.
This incident is so important that it is one of the few recorded in all four of the Gospels (Matthew, Mark, Luke and John). Two of them report Jesus saying that the story will be told forever, in memory of the woman. There are differences in how the four place the event chronologically and other details, but all affirm the message that God's mercy is available to anyone who recognizes it in Christ.
Luke sets the woman in contrast with a religious leader, who expects priggish adherence to religious purity standards. In the other Gospels, she is contrasted with Jesus' own disciples, who object to her lavishing expensive ointment on his feet. "It should have been sold to help the poor!" is their protest. So neither the moral legalist nor the liberal do-gooder come off well. Only the party crasher who recognized God's favor and mercy in Christ got it right.
And please, please, PLEASE note the order of things:
...her sins, which were many, have been forgiven; hence she has shown great love.
NOT "She showed me some love so I forgave her sins," but "She recognized God's mercy and so she was set free to show great love."
Because Jesus was there, she felt favor that made her unafraid of the other party guests. She walked into a room full of people who disdained her or, if "sinner" in this case meant prostitute, possibly bought her sinful services in secret while rejecting her in public.
Jesus says, "Your sins are forgiven" and "Your faith has saved you, go in peace" not as rewards for her foot washing, but as assurances to the woman and provocations to the others. Their failure to recognize God's favor in their midst is exposed as they begin to mutter, "Who is this who even forgives sins?"
Justification by faith is a challenge to those of other belief systems, who set up standards we must meet to earn God's favor or to somehow validate our lives.
But the doctrine also challenges the church, as we often bury this Good News under our hypocrisies, complexities and passing urgencies, hiding it from those who would be blessed to hear it.