From The Gospel of John, by Francis Martin and William Wright, commenting on John 8:1-11:
The story of Jesus and the woman caught in adultery (John 7:53–8:11) has a complicated history. It does not appear in any major Greek copy of John before the sixth century, which is why it appears in brackets in the NABRE, although it does appear in earlier Latin manuscripts. In some Greek manuscripts of John, the story appears in places other than its present location. One manuscript group has the account at the end of the Gospel, after 21:25. In addition, it appears in some manuscripts of the Gospel of Luke, after 21:38. The Greek language in this story differs noticeably from that in the rest of John. These factors suggest that the story did not originate with the rest of the Fourth Gospel. Rather, it resembles conflict stories found in the Synoptics. The Church receives this text as inspired Scripture and proclaims it liturgically on the fifth Sunday of Lent in Year C.
Jesus shows loving-kindness to a person involved in sexual immorality. Many men and women are in a similar situation today. Turning away from such sinful activity can be very difficult. The gentle mercy of Jesus, which is infinitely greater than the worst of our sins, is available to all in the sacrament of reconciliation, through which he pardons all our sins, even the most serious ones. Moreover, Christians who are not involved in such sinful behavior do well to avoid the proud self-righteousness of the woman’s accusers and instead imitate Jesus, not condemning but lovingly summoning the sinner to repent and live a better life.
Pope Francis on Christ’s Mercy:
[This] Gospel presents to us the episode of the adulterous woman ([John] 8:1–11), whom Jesus saves from being condemned to death. Jesus’ attitude is striking: we do not hear words of scorn, we do not hear words of condemnation, but only words of love, of mercy, which are an invitation to conversion. “Neither do I condemn you; go, and do not sin again” (v. 11). Ah! Brothers and Sisters, God’s face is the face of a merciful father who is always patient. Have you thought about God’s patience, the patience he has with each one of us? That is his mercy. He always has patience, patience with us, he understands us, he waits for us, he does not tire of forgiving us if we are able to return to him with a contrite heart. (Pope Francis, “Angelus,” March 17, 2013.)