Brothers and sisters:
If you are guided by the Spirit, you are not under the law.
Now the works of the flesh are obvious:
immorality, impurity, licentiousness, idolatry,
sorcery, hatreds, rivalry, jealousy,
outbursts of fury, acts of selfishness,
dissensions, factions, occasions of envy,
drinking bouts, orgies, and the like.
I warn you, as I warned you before,
that those who do such things will not inherit the Kingdom of God.
In contrast, the fruit of the Spirit is love, joy, peace,
patience, kindness, generosity,
faithfulness, gentleness, self-control.
Against such there is no law.
Now those who belong to Christ Jesus have crucified their flesh
with its passions and desires.
If we live in the Spirit, let us also follow the Spirit.
Paul alerts readers that a hidden war is waged in the heart of every Christian. It is a struggle between the Spirit and our flesh, i.e., our fallen nature that inclines us toward evil (Rom 8:5–8). Unless we follow the Spirit’s lead, the lusts of the flesh (concupiscence) will dominate our lives and enslave us in sin. When we respond to grace, we enable the Spirit to work powerfully in us by clearing out the vices that lead us away from God. Because of our weaknesses, victory in this struggle is possible but not easy (1 Cor 9:25–27) (CCC 2515–16; 1426; 2744).
5:19 works of the flesh: The sins of the flesh include more than just sins of the body (5:19–21). They consist of every act of immorality and injustice that stems from a disordered love of the world (Jas 4:1–5; 1 Jn 2:15–17). These grave sins sever offenders from Christ (Gal 5:4) and will block their entrance into heaven if repentance is neglected (CCC 1470, 1855).
5:21 shall not inherit the kingdom: Even Christians can forfeit their salvation if they stifle the Spirit and submit to the flesh (Rom 6:15–16). Paul posts this warning in several of his letters (Rom 8:12–13; 1 Cor 6:9–10; Eph 5:5).
5:22 the fruit of the Spirit: The indwelling of the Spirit produces holiness in the lives of believers (Mt 12:33; Jn 15:1–6). The first fruit of this divine presence is love, the source of all that is good and the virtue upon which others are built (Rom 5:5; 2 Cor 1:22). It may be significant that Paul says “fruit” (singular) instead of “fruits” (plural), suggesting that life in the Spirit is integrated and whole, not fragmented or divided (CCC 736, 1695, 1832).
5:24 crucified the flesh: Baptism unites believers with the saving death of Jesus, so much so that Paul says we are “crucified with Christ” (2:20; cf. Rom 6:3–4). In addition to receiving forgiveness, we die to our former way of life through the Spirit, who gives us new strength to master our passions and selfish desires (Rom 7:21–8:2) (CCC 2543, 2848).
“If we live in the Spirit, let us also follow the Spirit.”
When someone lets himself be led by his instincts he is said to be leading an “animal life”; whereas, if he acts as his reason advises, he is leading a rational, human, life. Similarly, when one allows the Holy Spirit to act, one’s life becomes life according to the Spirit—a supernatural life, a life which is no longer simply human but divine. This is what happens when a person is in the state of grace and is mindful of the treasure he bears within.
“Alone! You are not alone. We are keeping you close company from afar. Besides …, the Holy Spirit, living in your soul in grace—God with you—is giving a supernatural tone to all your thoughts, desires and actions” (St Josemaría Escrivá, The Way, 273).
The soul then becomes a good tree which is known by its fruits. Its actions reveal the presence of the Paraclete, and because of the spiritual delight they give the soul, these actions are called fruits of the Holy Spirit (cf. St Thomas Aquinas, Summa theologiae, 1–2, 70, 1).
“Those blessed fruits enumerated by the Apostle (Gal 5:22) the Spirit produces and shows forth in the just, even in this mortal life—fruits replete with all sweetness and joy. Such must, indeed, be from the Spirit ‘who in the Trinity is the love of the Father and the Son, filling all creatures with immeasurable sweetness’ (St Augustine, De Trinitate, 6, 9)” (Leo XIII, Divinum illud munus, 12).
May the virtues of faith, hope, and love go with you today – DV.
CCC Catechism of the Catholic Church
 The Ignatius Catholic Study Bible: The New Testament (San Francisco: Ignatius Press, 2010), 340–341.
 Saint Paul’s Letters to the Romans & Galatians, The Navarre Bible (Dublin; New York: Four Courts Press; Scepter Publishers, 2005), 169–170.