From the Word
3 So he told them this parable: 4 “What man of you, having a hundred sheep, if he has lost one of them, does not leave the ninety-nine in the wilderness, and go after the one which is lost, until he finds it? 5 And when he has found it, he lays it on his shoulders, rejoicing. 6 And when he comes home, he calls together his friends and his neighbors, saying to them, ‘Rejoice with me, for I have found my sheep which was lost.’ 7 Just so, I tell you, there will be more joy in heaven over one sinner who repents than over ninety-nine righteous persons who need no repentance.
Luke 15:3–7, RSV
This great and good Shepherd is not satisfied to seek his lost sheep so lovingly and carry it home so gently with joy; but when he brings it home he appoints a special feast and season of joy, and calls together his friends and neighbors to rejoice with him. Yea, he makes a great jubilee. Thus God in heaven together with all the heavenly hosts and all creatures rejoice over one sinner that repents. Here is shown who the lost sheep is, namely, the sinner who repents, that is, who feels his sins and is heartily sorry on account of them, and would gladly be free from them, come to Christ and amend his life. The character of Christ is such as to seek and carry no sheep except that which is lost and knows no refuge or help of its own.
How could Christ preach more effectively and comfortingly, or what more should he do to make the heart joyful and awaken a strong confidence in him? He is such a Shepherd as is not only unwilling to lose his sheep, but anxiously seeks it; and when he has found it, he carries it home with all joy, and instigates such a feast of joy that all the angels and saints in heaven and all creatures rejoice and smile so benignly that even the sun must shine more lovely. For when man is sorrowful, the sun and everything appears dark to him, but when the heart is joyful everything appears lighter and brighter to him.
He who will firmly believe Christ to be this kind Shepherd shall receive true consolation and joy in Christ the Lord; because he has here the promise, that if he cling unto Christ and permit himself to be carried on his shoulders, he is a dear guest in the kingdom of heaven and will be received with great joy. Therefore if you desire to possess true comfort and joy, learn to impress this lovely picture on your heart. In Christ you find all things, if you only remain under his protection and lie still upon his shoulders. You need not be troubled about sin, death or life, you have all things in Christ who carries and defends you.
Luther, Martin, and John Sander. Devotional Readings from Luther’s Works for Every Day of the Year. Augustana Book Concern, 1915, pp. 285–86.