1. In the Incarnation, God fully reveals himself in the Son who came into the world (cf. Tertio Millennio Adveniente, 9). Our faith is not simply the result of our searching for God. In Jesus Christ, it is God who comes in person to speak to us and to show us the way to himself.
The Incarnation also reveals the truth about man. In Jesus Christ, the Father has spoken the definitive word about our true destiny and the meaning of human history (cf. ibid., 5). “In this is love: not that we have loved God, but that he loved us and sent his Son as an expiation for our sins” (1 Jn 4:10). The Apostle is speaking of the love that inspired the Son to become man and to dwell among us. Through Jesus Christ we know how much the Father loves us. In Jesus Christ, by the gift of the Holy Spirit, each one of us can share in the love that is the life of the Blessed Trinity.
Saint John goes on: “Whoever acknowledges that Jesus is the Son of God, God remains in him and he in God” (1 Jn4:15). Through faith in the Son of God made man we abide in the very heart of God: “God is love, and whoever remains in love remains in God and God in him” (1 Jn 4:16). These words open to us the mystery of the Sacred Heart of Jesus: the love and compassion of Jesus is the door through which the eternal love of the Father is poured out on the world. In celebrating this Mass of the Sacred Heart, let us open wide our own hearts to God’s saving mercy!
2. In the Gospel reading which we have just heard, Saint Luke uses the figure of the Good Shepherd to speak of this divine love. The Good Shepherd is an image dear to Jesus in the Gospels. Answering the Pharisees who complained that he welcomed sinners by eating with them, the Lord asks them a question: Which of you, having a hundred sheep and losing one of them, would not leave the ninety-nine in the desert and go after the lost one until he finds it? “And when he does find it, he sets it on his shoulders with great joy and, upon his arrival home, he calls together his friends and neighbors and says to them: 'Rejoice with me because I have found my lost sheep'” (Lk15:5-6).
This parable highlights the joy of Christ and of our heavenly Father at every sinner who repents. God’s love is a love that searches us out. It is a love that saves. This is the love that we find in the Heart of Jesus.
[Pope John Paul II, homily in St Louis 27 January 1999]