“However, now in the light of the Gospel, we can clearly see who are those that Christ and the apostles called saints. They are not the ones who live alone and in celibacy or who abstain strictly regarding days, foods, dress, and other similar things or who externally appear to do great and monstrous works (as we read about many in Lives of the Fathers). Instead, it is those who, having been called by the Gospel and baptized, believe they have been sanctified and cleansed by Christ’s death and blood.
That is why Paul in his writings calls them saints, children and hears of God, and the like. Thus everyone who believes in Christ, whether it is man or woman, free or slave, all are saints. They are not saints through their own works but through God’s works such as His word, His sacraments, Christ’s passion, His death, His resurrection, His victory, and the outpouring of the Holy Spirit. In summary, they are holy through a holiness they freely receive. However, it’s not through a holiness that they themselves have achieved through their own productivity, good works, and merits. In brief, you are holy through a passive righteousness and not through an active righteousness.
“The ministers of the word, local judges, parents, children, teachers, and others are those who are truly saints – that is, if first and foremost, they possess full assurance that Christ is their wisdom, righteousness, sanctification, and redemption, and second, they fulfill the duty of their vocation according to what is ordered in God’s word and do not humor the flesh, restraining their lustful longings through the Spirit.
Although not all have the same strength to resist temptation but in most people their weakness and frailties are obvious, these do not hinder their holiness. Thus their sins do not proceed from a will determined to do what is evil but only from weakness and frailty, for (as I’ve said before) the faithful indeed do feel the desires and lusts of the flesh, but they resist so that they don’t satisfy its desires. Further, if at any time, they unbecomingly fall into sin, even so, they obtain forgiveness if by faith they rise up again unless we push them away. Instead, let us seek them out and bring them home as stray and lost sheep. Thus God forbid that I immediately judge the weak in their faith and morals, supposing they are profane or wicked, when it is obvious they love and revere God’s works; they come to the Lord’s Supper, for God has received them and counts them as righteous through the remission of sins. That is how they stand or fall. This how Paul speaks everywhere about the saints.”
~Martin Luther’s Commentary on Saint Paul’s Epistle to the Galatians (1535), transl. by Haroldo Camacho (2018), Gal. 5:16-24; p. 474.