Tax collectors and sinners were all drawing near to listen to Jesus,
but the Pharisees and scribes began to complain, saying, "This man welcomes sinners and eats with them."
So to them he addressed this parable.
"What man among 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.'
I tell you, in just the same way there will be more joy in heaven over one sinner who repents than over ninety-nine righteous people who have no need of repentance."
Or what woman having ten coins and losing one would not light a lamp and sweep the house, searching carefully until she finds it?
And when she does find it, she calls together her friends and neighbors and says to them, 'Rejoice with me because I have found the coin that I lost.'
In just the same way, I tell you, there will be rejoicing among the angels of God over one sinner who repents."
Then he said, "A man had two sons,
and the younger son said to his father, 'Father, give me the share of your estate that should come to me.' So the father divided the property between them.
After a few days, the younger son collected all his belongings and set off to a distant country where he squandered his inheritance on a life of dissipation.
When he had freely spent everything, a severe famine struck that country, and he found himself in dire need.
So he hired himself out to one of the local citizens who sent him to his farm to tend the swine.
And he longed to eat his fill of the pods on which the swine fed, but nobody gave him any.
Coming to his senses he thought, 'How many of my father's hired workers have more than enough food to eat, but here am I, dying from hunger.
I shall get up and go to my father and I shall say to him, "Father, I have sinned against heaven and against you.
I no longer deserve to be called your son; treat me as you would treat one of your hired workers."'
So he got up and went back to his father. While he was still a long way off, his father caught sight of him, and was filled with compassion. He ran to his son, embraced him and kissed him.
His son said to him, 'Father, I have sinned against heaven and against you; I no longer deserve to be called your son.'
But his father ordered his servants, 'Quickly bring the finest robe and put it on him; put a ring on his finger and sandals on his feet.
Take the fattened calf and slaughter it. Then let us celebrate with a feast,
because this son of mine was dead, and has come to life again; he was lost, and has been found.' Then the celebration began.
Now the older son had been out in the field and, on his way back, as he neared the house, he heard the sound of music and dancing.
He called one of the servants and asked what this might mean.
The servant said to him, 'Your brother has returned and your father has slaughtered the fattened calf because he has him back safe and sound.'
He became angry, and when he refused to enter the house, his father came out and pleaded with him.
He said to his father in reply, 'Look, all these years I served you and not once did I disobey your orders; yet you never gave me even a young goat to feast on with my friends.
But when your son returns who swallowed up your property with prostitutes, for him you slaughter the fattened calf.'
He said to him, 'My son, you are here with me always; everything I have is yours.
But now we must celebrate and rejoice, because your brother was dead and has come to life again; he was lost and has been found.'"

Gospel commentary

Saint Ambrose (c.340-397), Bishop of Milan and Doctor of the Church
On St Luke's Gospel, 7, 207 (SC 52)

Since man's weakness is incapable of maintaining a firm step in this changing world, the good doctor shows you a remedy against going astray and the merciful judge does not withhold hope of forgiveness. It is not without reason that Saint Luke put forward three parables in succession: the sheep who strayed and was found again; the coin that was lost and found; the son who died and came back to life. This is so that this threefold remedy will urge us to take care of our wounds… The weary sheep is brought back by the shepherd; the lost coin is found; the son turns back and returns to his father, repenting of his waywardness…

Let us rejoice, then, in that this sheep, which went astray in Adam, has been raised up again in Christ. Christ's shoulders are the arms of the cross; there it is that I have laid down my sins; on that gallows I have found my rest. This “sheep” is one according to its nature but not in personality since all form a single body composed of many in members. That is why it is written: “You are Christ's body and individually parts of it,” (1Cor 12:27). “The Son of Man has come to save what was lost” (Lk 19:10), that is to say everyone, since “just as in Adam all die, so too in Christ shall all be brought to life” (1Cor 15:22)…

Nor is it irrelevant that the woman rejoices to have found her coin: it is no small thing, this coin on which is portrayed the image of a prince. In the same way, the good of the Church is the image of the King. We are sheep: let us then pray the Lord to lead us to restful waters (Ps 22[23]:2). We are sheep: let us ask for pasture. We are the coin: let us keep our value. We are sons: let us run to the Father.